Chapter VII: Part I: The Individual Organism with Regard to Form and Metabolism (4)

We know that we may take off any part of the whole, as to quantity, and that a proportionate embryo will result, unless the part removed is of a very large size. This means that the prospective value of any element certainly depends on, certainly is a function of, the *absolute size* of the actually existing part of our system in the particular case. Let *s* be the absolute size of the system in any actual experimental case of morphogenesis: then we may write *p.v. (X) = f(s ... )*. But we shall have to add still some other letter to this *s*.

The operation of section was without restriction either as to the amount of the material removed from the germ, or as to the direction of the cut. Of course, in almost every actual case there will be both a definite size of the actual system and a definite direction of the cut going hand-in-hand. But in order to study independently the importance of the variable direction alone, let us imagine that we have isolated at one time that part of our system which is bounded by the lines *a_1 b_1*, and at another time an equal amount of it which has the lines *a_2 b_2* as its boundaries. Now since in both cases a typical small organism may result on development, we see that, in spite of their equal size the prospective value of every element of the two pieces cut out of the germ may vary even in relation to the direction of the cut itself. Our element, *X*, may belong to both of these pieces of the same size: its actual fate nevertheless will be different. Analytically, it may be said to change in correspondence to the actual position of the actual boundary lines of the piece itself with regard to the fundamental lines of orientation, *a* and *b*; let this actual position be expressed by the letter *l*, *l* marking the distance of one[58] of the actual boundary lines of our piece from *a* or *b*: then we are entitled to improve our formula by writing *p.v. (X) = f(s, l ... )* (Fig. 11).

[58] The distance of the other boundary line from *a* or *b* would be given by the value of *s*.

The element *X* forms part of the systems *a b* or *a_1 b_1* or *a_2 b_2*; its prospective value is different in each case.]

But the formula is not yet complete: *s* and *l* are what the mathematicians call variables: they may have any actual value and there will always be a definite value of *p.v.*, *i.e.* of the actual fate which is being considered; to every value of *s* and *l*, which as we know are independent of each other, there corresponds a definite value of the actual prospectivity. Now, of course, there is also a certain factor at work in every actual case of experimental or normal development, which is *not* a variable, but which is the same in all cases. This factor is a something embraced in the prospective potency of our system, though not properly identical with it.

The prospective potency of our system, that is to say of each of its elements, is the sum total of what can be done by all; but the fact that a typically proportionate development occurs in every possible case, proves that this sum comes into account, not merely as a sum, but as a sort of order: we may call this order the “relation of localities in the absolutely normal case.” If we keep in mind that the term “prospective potency” is always to contain this order, or, as we may also call it, this “relative proportionality,” which, indeed, was the reason for calling our systems “harmonious,” then we may apply it without further explanation in order to signify the *non-variable* factor on which the prospective value of any element of our systems depends, and, if we denote the prospective potency, embracing order, by the letter *E*, we are now able to complete our formula by saying *p.v. (X) = f(s, l, E)*. So far the merely analytical study of the differentiation of harmonious-equipotential systems.[59]

[59] A far more thorough analysis of this differentiation has been attempted in my paper, “Die Localisation morphogenetischer Vorgänge. Ein Beweis vitalistischen Geschehens,” Leipzig, 1899.

*Instances of “Harmonious-Equipotential Systems”*

We must try at first to learn a few more positive facts about our systems, in order that we may know how important is the part which they play in the whole animal kingdom, and in order that our rather abstract analysis may become a little more familiar to us. We know already that many of the elementary morphogenetic organs have been really proved to be harmonious-equipotential systems, and that the same probably is true of many others; we also know that the immature egg of almost all animals belongs to this type, even if a fixed determination of its parts may be established just after maturation. Moreover, we said, when speaking about some new discoveries on form-restitution, that there are many cases in which the processes of restitution do not proceed from single localities, the seat of complex potencies in the organism, but in which each *single* part of the truncated organism left by the operation has to perform one *single* act of restoration, the full restitution being the result of the totality of all. These cases must now be submitted to a full analysis.

All of you have seen common sea-anemones or sea-roses, and many of you will also be familiar with the so-called hydroid polyps. *Tubularia* is one genus of them: it looks like a sea-anemone in miniature placed on the top of a stem like a flower. It was known already to Allman that *Tubularia* is able to restore its flower-like head when that is lost, but this process was taken to be an ordinary regeneration, until an American zoologist, Miss Bickford, succeeded in showing that there was no regeneration process at all, in the proper sense of the word, no budding of the missing part from the wound, but that the new tubularian head was restored by the combined work of many parts of the stem. Further analysis then taught us that *Tubularia* indeed is to be regarded as the perfect type of an harmonious-equipotential system: you may cut the stem at whatever level you like: a certain length of the stem will always restore the new head by the co-operation of its parts. As the point of section is of course absolutely at our choice, it is clear, without any further discussion, that the prospective value of each part of the restoring stem is a “function of its position,” that it varies with its distance from the end of the stem; and so at once we discover one of the chief characteristics of our systems. But also the second point which enters into our formula can be demonstrated in *Tubularia*: the dependence of the fate of every element on the actual size of the system. You would not be able to demonstrate this on very long stems, but if you cut out of a *Tubularia* stem pieces which are less than ten millimetres in length, you will find the absolute size of the head restored to be in close relation to the length of the stem piece, and this dependence, of course, includes the second sort of dependence expressed in our formula.

The figures will serve to show you a little more concretely what has been described. The head of *Tubularia* consists of a sort of broad base with a thin proboscis upon it, both bearing a large number of tentacles; these tentacles are the first things to be seen as primordia (“Anlagen”) in the process of restitution. You notice two rings of longitudinal lines inside the stem; the lines will become walls and then will separate from the stem until they are only connected with it at their basal ends; the new tentacles are ready as soon as that has happened, and a process of growth at the end will serve to drive the new head out of the so-called perisarc or horny skeleton, which surrounds the stem. By comparing the two figures, 12 *e*, and *g*, you easily find out that the absolute lengths of the two tentacle rings are very different, and that both are in proportion[60] to the actual size of the stem (Fig. 12).

[60] This statement is *not strictly* correct for *Tubularia*. I found (*Archiv f. Entwickelungsmechanik*, ix. 1899), that a reduction of the length of the stem is always followed by a reduction of the size of the hydranth-primordium, but there is no real proportionality between them. It is only for theoretical simplification that a strict proportionality is assumed here, both in the text and the diagram. But there is an almost strict proportionality in all cases of “closed forms.”

*a.* Diagram of the “Hydranth,” with its short and long tentacles.

*b.* Restitution of a new hydranth inside the perisarc (*p*).

*c.* The same--later stage; the tentacles are complete; the whole hydranth will be driven out of the perisarc by a process of growth that occurs at the locality marked ⬆.

*d.* A stem of *Tubularia* cut either at *a_1 b_1* or at *a_2 b_2*, or at *a_1 c*.

*e.* Position of tentacles in the piece cut at *a_1 b_1*.

*f.* Position of tentacles in the piece cut at *a_2 b_2*, which is equal in length to *a_1 b_1*.

*g.* Position of tentacles in the piece cut at *a_1 c*, which is half as long as *a_1 b_1*.]

So we find our formula *p.v. (X) = f(s, l, E)* very well illustrated in *Tubularia*. The formula indeed may help us to predict, in any case, where a certain part of the polyp’s organisation is to originate, at least if we know all that is included under our letter *E*, *i.e.* the normal proportion of our form. Of course such prediction would not have much practical importance in all our cases of morphogenesis, but nevertheless I should like to state here that it is possible; for many scientific authors of recent times have urged the opinion that prediction of, and domination over, what will happen, can be the only true aims of sciences at all. I myself judge these aims to be of second or third-rate importance only, but, if they may be reached by what our purely theoretical study teaches, so much the better.

Another very typical case of a morphogenetic system of the harmonious type is supplied by the phenomena of restoration in the ascidian *Clavellina*. I cannot fully describe the organisation of this form (Fig. 13a), and it must suffice to say that it is very complicated, consisting of two very different chief parts, the branchial apparatus and the so-called intestinal sac; if these two parts of the body of *Clavellina* are separated one from the other, each may regenerate the other in the typical way, by budding processes from the wound. But, as to the branchial apparatus, there may happen something very different: it may lose almost all of its organisation and become a small white sphere, consisting only of epithelia corresponding to the germ-layers, and of mesenchyme between them, and then, after a certain period of rest, a new organisation will appear. Now this new organisation is not that of a branchial apparatus but represents a very small but complete ascidian (Fig. 13). Such a fact certainly seems to be very important, not to say very surprising; but still another phenomena may be demonstrated on the animal which seems to be even more important. You first isolate the branchial apparatus from the other part of the body, and then you cut it in two, in whatever direction you please. Provided they survive and do not die, as indeed many of them do, the pieces obtained by this operation will each lose their organisation, as did the whole branchial apparatus, and then will each acquire another one, and this new organisation is also that of a *complete* little *Clavellina*. So we see that not only is the branchial apparatus of our animal capable of being transformed into a whole animal by the co-operative work of all its parts, but even each part of it may be transformed into a small *whole*, and it is quite at our disposal how large this part shall be, and what sort of a fragment of the original branchial apparatus it shall represent.

*a.* Diagram of the normal animal: *E* and *J* = openings; *K* = branchial apparatus; *D* = intestine; *M* = stomach; *H* = heart.

*b.* The isolated branchial apparatus.

*c-e.* Different stages of reduction of the branchial apparatus.

*f.* The new *whole* little ascidian.]

We could hardly imagine a better instance of an harmonious-equipotential system.

I cannot give you a description of all the other types of our systems subservient to restitution, and I can only mention here that the common hydra and the flatworm *Planaria* are very fine examples of them. But to one special case of harmonious equipotentiality you must allow me to direct your further attention.

It has been known for many years that the Protozoa are also capable of a restoration of their form and organisation after disturbances, if at least they contain a certain amount of their nuclear substance. This process of restoration used to be regarded as belonging to the common type of regeneration proper, until T. H. Morgan succeeded in showing that in the genus *Stentor* it follows just the very lines which we know already from our study of embryonic organs or from *Tubularia*; that an harmonious-equipotential system is at the basis of what goes on. Now, you know that all Protozoa are but one highly organised cell: we have therefore here an instance where the so-called “elements” of our harmonious-morphogenetic system are not cells, but something inside of cells; and this feature must appear to be of very great moment, for it first shows, as we have already pointed out on another occasion, that morphogenesis is not dependent on cell-division, and it states at the same time that our concept of the harmonious-equipotential system may cover a very great area--that, in fact, it is a scheme of a very wide extent.

*The Problem of the Factor* E

We turn back again to considerations of a more abstract form. We left our analysis of the differentiation of the harmonious-equipotential systems, and particularly of the phenomena of localisation during this differentiation, at the point where we had succeeded in obtaining an equation as the expression of all those factors on which the prospective value, the actual fate, of any element of our systems depends, *p.v. (X) = f(s, l, E)* was the short expression of all the relations involved; *s* and *l*, the absolute size of the system and the relative position of the element with respect to some fixed points, were independent variables; *E* was a constant, namely, the prospective potency, with special regard to the proportions embraced by it.

We shall now study the significance of the factor *E*.

What does this *E* mean? Is it a short expression merely for an actual sum of elemental agents having a common resultant? And, if so, of what kind are these agents? Or what may *E* mean, if it can be shown *not* to be a short sign for a mere sum?

*No Explanation Offered by “Means” or “Formative Stimuli”*

For practical purposes it seems better if we modify the statement of our question. Let us put it thus: *E* is one of the factors responsible, among variables, for the localisation of organic differentiation; what then do we actually know about the causal factors which play a localising part in organogenesis? We, of course, have to look back to our well-studied “formative stimuli.” These stimuli, be they “external” or “internal,” come from without with respect to the elementary organ in which any sort of differentiation, and therefore of localisation, occurs: but in our harmonious systems no localising stimulus comes from without, as was the case, for instance, in the formation of the lens of the eye in response to the optical vesicle touching the skin. We know absolutely that it is so, not to speak of the self-evident fact that the general “means” of organogenesis have no localising value at all.[61]

[61] One might object here that in a piece of a *Tubularia* stem, for instance, the tissues are in direct contact with the sea-water at the two points of the wounds only, and that at these very points a stimulus might be set up--say by a process of diffusion--which gradually decreases in intensity on its way inward. And a similar argument might apply to the small but whole blastula of Echinus, and to all other cases. But, in the first place, stimuli which only differ in intensity could hardly call forth the typical and typically localised single features realised in differentiation. On the other hand--and this will overthrow such an hypothesis completely--the dependence of the single localised effects in every case on the *absolute size* of the fragment or piece chosen for restoration renders quite impossible the assumption that all the singularities in the differentiation of the harmonious systems might be called forth by single stimuli originating in two fixed places in an *independent* way. These would never result in any “harmonious,” any proportionate structure, but a structure of the “normal” proportionality *and size* at its two ends and non-existent in the middle!

So we see there is nothing to be done, either with the means or with the formative stimuli; both are entirely unable to account for those kinds of localisation during differentiation which appear in our harmonious systems.

But is there no possibility of explaining the phenomena of organogenetic localisation by any other sort of interaction of parts? Two such possibilities may at the first glance seem to exist.

*No Explanation Offered by a Chemical Theory of Morphogenesis*

Though never set forth, in the form of a properly worked-out theory, the view has sometimes been advocated by biologists, that a chemical compound of a very high degree of complication might be the very basis of both development and inheritance, and that such a chemical compound by its disintegration might direct morphogenesis.

Let us first examine if such a view may hold for the most general features of organic morphogenesis. It seems to me that from the very beginning there exists one very serious objection to every chemical theory of form-building, in the mere fact of the possibility of the restoration of form starting from atypical localities. The mere fact, indeed, that there is such a thing as the regeneration of a leg of a newt--to say nothing about restitution of the harmonious type--simply contradicts,[62] it seems to me, the hypothesis, that chemical disintegration of one compound may govern the course of morphogenetic events: for whence comes the re-existence of the hypothetical compound, newly to be disintegrated, after disintegration *has* been completed once already? And we even know that regeneration may go on several times running from the same locality!

[62] See my article in *Biolog. Centralblatt*, 27, 1907, p. 69. The question is rendered still more complicated by the fact that in the case of the regeneration, say, of a leg it is not the original “morphogenetic compound” which is again required for disintegration, after it has become disintegrated once already, but only a specific part of it: just that part of it which is necessary for producing the leg! On the other hand, it would be impossible to understand, on the basis of physical chemistry, how the isolated branchial apparatus of *Clavellina* could be transformed, by chemical processes exclusively, into a system of which only a certain *part* consists of that substance of which the starting-point had been composed in its *completeness*.

But, if we intentionally disregard this difficulty, in spite of its fundamental character, how could the hypothesis of chemical disintegration give the reason for the differentiation of our harmonious-equipotential systems, with special regard to the localisation of it; how could it account, in other words, for the appearance of typically localised specifications in an organ for which no external localising causes can be predicated?

Let us remember that a few original intimate differences exist in our harmonious systems: the main directions of the intimate protoplasmic structure including polarity and bilaterality. There are therefore three times two specified poles in each of these systems, at least in bilateral organisms, but no other differences are present in them. A few very simple cases of harmonious differentiation might indeed be understood on the theory of a disintegrating chemical compound in connection with these few differences. Imagine that the original compound, of the quantity *a*, is disintegrated to the amount of *a*_1; from *a*_1 are formed the two more simple compounds, *b* and *c*, both of them in definite quantities; then we have the three chemical individuals, *a-a*_1, *b* and *c*, as the constituents of our harmonious system; and it now might be assumed, without any serious difficulty, though with the introduction of some new hypotheses, that the two poles of one of the fundamental axes of symmetry attract *b* and *c* respectively, *a-a*_1 remaining unattracted between them. We thus should have the three elementary constituents of the system separated into three parts, and as they all three are of a definite quantity, their separation would mean that the system had been divided into three parts, *a-a*_1, *b* and *c*, also with regard to its proper form. It is clear, that by taking away any part of the original system, by means of operations, there would be taken away a certain amount of the original compound; say that *a/n* is left; then, of course, the three constituents after the partial disintegration would be *a-a_1/n*, *b/n* and *c/n*, and so it follows that the proportionality of localisation would really be preserved in any case.

But these considerations, evident as they seem to be in the most simple case, fail to satisfy in a really general sense: for two different reasons. First, they could never account for the fact that the differentiated organism by no means consists of so many different compounds as it shows single parts of its differentiation, but that, on the contrary, it only consists, as we know, of a certain rather limited number of true different morphogenetic elements, these elements occurring again and again--as for instance, nervous or muscular elements--but typical each time in locality, quantity, and form. And in the second place, the very *form* of elementary organs, their form as such, does not at all go hand-in-hand with chemical differences; this feature alone would absolutely overthrow any sort of a chemical morphogenetic theory to account for the problem of localisation. Take the typically arranged ring of the mesenchyme cells in our Echinus-gastrula, with its two spherical triangles, so typically localised; look at any sort of skeleton, in Radiolaria, or in starfishes, or in vertebrates: here you have form, real form, but form consisting of only one material. Not only is the arrangement of the elements of form typical here, *e.g.* the arrangement of the single parts of the skeleton of the hand or foot, but also the special form of each element is typical, *e.g.* the form of each single bone of the foot; and, on a purely chemical theory of morphogenesis the sufficient reason for the production of typical form in such a sense would be wanting. For atoms or molecules by themselves can only account for form which is arranged, so to speak, according to spatial geometry--as in fact they do in crystallography; but they can never account for form such as the skeleton of the nose, or hand, or foot. You will answer me perhaps, that there may be non-chemical agents in the germ,[63] responsible for typical form-localisation, but by such reasoning you would be departing from a purely chemical theory. Our next paragraph will be devoted to this side of the question.

[63] Besides the specified poles determined by the polar-bilateral structure of the protoplasm.

That is the principal reason for rejecting all sorts of chemical morphogenetic theories put forward to explain the problem of localisation; it is more explicit, and therefore, I suppose, still more convincing than the more general consideration that the very fact of restitutions in itself must contradict the hypothesis that a disintegration of compounds might be the directive agency in morphogenesis. To sum up: Specificity of organic form does not go hand-in-hand with specificity of chemical composition, and therefore cannot depend on it; and besides that, specific organic form is such that it can never be explained by atomic or molecular arrangement in the chemical sense; for, to state it in a short but expressive manner, the “form” of an atom or molecule can never be that of a lion or a monkey. To assume that would be to go beyond the limits of chemistry in chemistry itself.

*No Machine Possible Inside the Harmonious Systems*

And now we turn to the last possibility which is left to us in our endeavour to “understand” the localisation of the differentiation in our harmonious-equipotential systems by the means of physics and chemistry. Outside causes have failed to account for it, chemical disintegration of a compound has failed too. But could there not exist some sort of complicated interactions amongst the parts of the harmonious system themselves? Could there not exist some kind of a real machine in the system, which, if once set going, would result in the differentiations that are to take place? Then we might say that the “prospective potency” of the system is in fact that machine; we should know what the letter *E* of our equation stood for: viz., a resultant action of many complicated elemental interactions, and nothing more.

Weismann, we know already, had assumed that a sort of machine was the prime mover of morphogenesis. We have seen that his theory cannot be true; the results of experiments most strongly contradict it. But, of course, the experiments only showed us that *such* a machine as *he* had imagined to exist could not be there, that development could not be governed by the disintegration of a given complicated structure into its simplest parts. But might not some other machine be imaginable?

We shall understand the word “machine” in a most general sense. A machine is a typical configuration of physical and of chemical constituents, by the acting of which a typical effect is attained. We, in fact, lay much stress upon embracing in our definition of a machine the existence of chemical constituents also; we therefore understand by the word “machine” a configuration of a much higher degree of complication than for instance a steam-engine is. Of course a machine, whose acting is to be typical with regard to the three dimensions in space, has to be typically constructed with regard to these three dimensions itself; a machine that was an arrangement of elements in a strict plane could never have typical effects at right angles to that plane. This is a point which must well be kept in mind in all hypothetical considerations about machines that claim to explain morphogenesis.

It must be granted that a machine, as we understand the word, might very well be the motive force of organogenesis in general, if only normal, that is to say, if only undisturbed development existed, and if a taking away of parts of our systems led to fragmental development.

But we know that, at least in our harmonious-equipotential systems, quite another process occurs after parts have been taken away: the development that occurs is not fragmental but whole, only on a smaller scale.

And we know, further, that this truly whole development sets in irrespective of the amount and direction of the separation. Let us first consider the second of these points. There may be a whole development out of each portion of the system--above certain limits--which is, say, of the volume *V*. Good! Then there ought to exist a machine, like that which exists in the whole undisturbed system, in this portion *V* also, only of smaller dimensions; but it also ought to exist in the portion *V*_1 which is equal to *V* in amount, and also in *V*_2, in *V*_3, *V*_4 and so on. Indeed, there do exist almost indefinitely many *V*_n all of which can perform the whole morphogenesis, and all of which therefore ought to possess the machine. But these different portions *V*_n are only partly different from each other in spatial relation. Many parts of *V*_2 are also parts of *V*_1 and of *V*_3 and of *V*_4 and so on; that is to say, the different volumes *V*_n overlap each other successively and in such a manner that each following one exceeds the preceding one in the line by a very small amount only. But what then about our machines? Every volume which may perform morphogenesis completely must possess the machine in its totality. As now every element of one volume may play any possible elemental rôle in every other, it follows that each part of the whole harmonious system possesses any possible elemental part of the machine equally well, all parts of the system at the same time being constituents of different machines.

A very strange sort of machine indeed, which is the same in all its parts (Fig. 14)!

According to the “machine-theory” of life this system ought to possess a certain unknown very complicated machine *in its completeness*:

(*a*) in its total length,
and (*b*) in each of the equal volumes *v*, *v*_1, *v*_2, *v*_3 and
so on,
and (*c*) in each of the unequal volumes *w*, *x*, *y*, and so on,
and (*d*) in every imaginable volume, no matter of what size.

Therefore the “machine-theory” of life is absurd.]

But we have forgotten, I see, that in our operation the absolute amount of substance taken away from the system was also left to our choice. From this feature it follows that not only all the different *V*_n, all of the same size, must possess the hypothetic machine in its completeness, but that all amounts of the values *V*_n-*n*, *n* being variable, must possess the totality of the machine also: and all values *V*_n-*n*, with their variable *n*, may again overlap each other.

Here we are led to real absurdities!

But what is the conclusion of our rather wild considerations?

It seems to me that there is only one conclusion possible. If we are going to explain what happens in our harmonious-equipotential systems by the aid of causality based upon the constellation of single physical or chemical factors and events, there *must* be some such thing as a machine. Now the assumption of the existence of a machine proves to be absolutely absurd in the light of the experimental facts. *Therefore there can be neither any sort of a machine nor any sort of causality based upon constellation underlying the differentiation of harmonious-equipotential systems.*

For a machine, typical with regard to the three chief dimensions of space, cannot remain itself if you remove parts of it or if you rearrange[64] its parts at will.

[64] The pressure experiments and the dislocation experiments come into account here; for the sake of simplicity they have not been alluded to in the main line of our argument.

Here we see that our long and careful study of morphogenesis has been worth while: it has afforded us a result of the very first importance.

*The Autonomy of Morphogenesis Proved*

No kind of causality based upon the constellations of single physical and chemical acts can account for organic individual development; this development is not to be explained by any hypothesis about configuration of physical and chemical agents. Therefore there must be something else which is to be regarded as the sufficient reason of individual form-production. We now have got the answer to our question, what our constant *E* consists in. It is not the resulting action of a constellation. It is not only a short expression for a more complicated state of affairs, it expresses *a true element of nature*. Life, at least morphogenesis, is not a specialised arrangement of inorganic events; biology, therefore, is not applied physics and chemistry: life is something apart, and biology is an independent science.

All our results at present, indeed, are negative in their form; our evidence was throughout what is called *per exclusionem*, or indirect or apagogic. There were excluded from a certain number of possibilities all except one; a disjunctive proposition was stated in the form: *E* is either this, or that, or the other, and it was shown that it could not be any of all these except one, therefore it was proved to be that one. Indeed, I do not see how natural science could argue otherwise; no science dealing with inorganic phenomena does; something new and elemental must always be introduced whenever what is known of other elemental facts is proved to be unable to explain the facts in a new field of investigation.

We shall not hesitate to call by its proper name what we believe we have proved about morphogenetic phenomena. What we have proved to be true has always been called *vitalism*, and so it may be called in our days again. But if you think a new and less ambitious term to be better for it, let us style it the doctrine of the *autonomy of life*, as proved at least in the field of morphogenesis. I know very well that the word “autonomy” usually means the faculty of *giving* laws to oneself, and that in this sense it is applied with regard to a community of men; but in our phrase autonomy is to signify the *being subjected* to laws peculiar to the phenomena in question. This meaning is etymologically defensible, and besides that I perhaps may remind you of a certain chapter of Professor Ward’s Gifford Lectures, in which he holds the view that, psychologically and epistemologically, there is more than a mere verbal relation between the civil and the natural “law.”

Vitalism then, or the autonomy of life, has been proved by us indirectly, and cannot be proved otherwise so long as we follow the lines of ordinary scientific reasoning. There can indeed be a sort of direct proof of vitalism, but now is not the time to develop this proof, for it is not of the purely scientific character, not so naïve as our present arguments are, if you choose to say so. An important part of our lectures next summer will be devoted to this direct proof.

“*Entelechy*”

But shall we not give a name to our vitalistic or autonomous factor *E*, concerned in morphogenesis? Indeed we will, and it was not without design that we chose the letter *E* to represent it provisionally. The great father of systematic philosophy, Aristotle, as many of you will know, is also to be regarded as the founder of theoretical biology. Moreover, he is the first vitalist in history, for his theoretical biology is throughout vitalism; and a very conscious vitalism indeed, for it grew up in permanent opposition to the dogmatic mechanism maintained by the school of Democritus.

Let us then borrow our terminology from Aristotle, and let that factor in life phenomena which we have shown to be a factor of true autonomy be called *Entelechy*, though without identifying our doctrine with what Aristotle meant by the word έντελέχεια. We shall use this word only as a sign of our admiration for his great genius; his word is to be a mould which we have filled and shall fill with new contents. The etymology of the word ἐντελέχεια allows us such liberties, for indeed we have shown that there is at work a something in life phenomena “which bears the end in itself,” ὃ ἔχει ἐν ἑαυτᾣ τὸ τέλος.

Our concept of entelechy marks the end of our analysis of individual morphogenesis. Morphogenesis, we have learned, is “epigenesis” not only in the descriptive but also in the theoretical sense: manifoldness in space is produced where no manifoldness was, real “evolutio” is limited to rather insignificant topics. But was there nothing “manifold” previous to morphogenesis? Nothing certainly of an *extensive* character, but there was something else: there was entelechy, and thus we may provisionally call entelechy an “*intensive manifoldness*.” That then is our result: not evolutio, but epigenesis--“epigenesis vitalistica.”

*Some General Remarks on Vitalism*

We now shall leave entelechy where it stands: next summer we shall turn back to it and shall make its full logical and ontological analysis our chief study. At present we are satisfied with having proved its existence in nature, with having laid some of the foundations of a doctrine to be based upon it. I hope that these foundations will evince themselves strong: that is all-important.[65] It indeed has been the fault of all vitalism in the past that it rested on weak foundations. Therefore the discussion of the basis underlying our doctrine of the autonomy of life is to occupy us still a considerable time. We shall devote to it two more of this year’s lectures and three of the next; we shall examine all sorts of phenomena of life in order to find out if there are any further proofs of vitalism, independent perhaps, of what we way call our *first proof*, which is based upon the analysis of the *differentiation of harmonious-equipotential systems*. We shall find some more independent proofs; and besides that we shall find many kinds of phenomena upon which future times perhaps may erect more of such independent proofs.

[65] My “first proof of vitalism” was first developed in the paper, “Die Localisation morphogenetischer Vorgänge,” Leipzig, 1899. (See additional remarks in *Organische Regulationem*, Leipzig, 1901, and in *Archiv für Entwickelungsmechanik*, 14, 1902.) I cannot admit that any really serious objection has been brought forward against it. (See my articles in *Biologisches Centralblatt*, 22, 23, 27, and in *Ergebnisse d. Anat. u. Entwickelungsgesch*. 11, 14.) An historical sketch of vitalism will be found in my book, *Der Vitalismus als Geschichte und als Lehre*, Leipzig, 1905.

For we shall be chary of bestowing the name “proof” except on what is a proof indeed, of course according to our critical conviction. Vitalistic views in biology have arisen in rather numerous forms during the last fifteen years, especially in Germany--though in very strong contrast to the so-called official German biology--but I can only admit that one of all the arguments of “neo-vitalism” has proved its statements. I refer to the theory of “morphaesthesia” as developed by Noll, which we shall study briefly in the next lecture. I cannot concede that Reinke or Schneider or Pauly have really proved what they believe, and I cannot even allow to the most original thinker in this field, Gustav Wolff, that he has given a real demonstration of his views. He states that the existence of so-called “primary purposefulness,” that is, the existence of adaptive processes, which cannot be imagined to have arisen on Darwinian principles, is able to prove vitalism; but I say that it only proves teleology, which is a broader concept than vitalism.

The possibility of a machine at the root of the phenomena in question always has to be excluded in order that vitalism may be proved, and I cannot grant that the necessity of such an exclusion has been actually shown by any of my fellow-combatants against so-called mechanism, except Noll.[66]

[66] We are dealing here with morphogenesis and so-called vegetative physiology only; to certain psychologists, who have refuted the theory of psycho-physical parallelism, I must grant that they also have proved vitalism. (See Volume II.)

*The Logic of our First Proof of Vitalism*

Let us devote the end of our present lecture to an account of the logical means by which it has been possible to develop what we hope will be regarded as a true *proof* of life autonomy.

Firstly, we have looked upon the phenomena of morphogenesis without any prepossessions; we may say that we have fully surrendered ourselves to them; we have not attacked them with any sort of dogmatism except the inherent dogmatism of all reasoning. But this dogmatism, if it may be called so, does not postulate that the results of the inorganic doctrines must hold for the organic world, but only that both the inorganic and the organic must be subject to certain most general principles.

By studying life as a given phenomenon, by fully devoting ourselves to our problem, we not only have analysed into its last elements what was given to us as our subject, but we also, more actively, have created new combinations out of those elements: and it was from the discussion of these positive constructions that our argument for vitalism was derived.

We have analysed morphogenesis into elementary processes, means, potency, formative stimulus, just as the physicist analyses mechanics into time, velocity, mass, and force; we have then rearranged our elements into “systems”--the equipotential systems, the harmonious-equipotential system in particular, just as the physicist composes his elements into the concepts of momentum or of kinetic energy or of work. And finally, we have discussed our compositions and have obtained our result, just as the physicist gets his ultimate results by discussing work and kinetic energy and momentum.

Of course the comparison is by no means intended to show that mechanics and biology are sciences of the same kind. In my opinion, they are not so at all; but nevertheless there do exist similarities of a logical kind between them.

And it is not the formal, logical character alone which allows us to compare biology with other natural sciences: there is still something more, there is one kind of assumption or postulate, or whatever you may choose to call it, without which all science whatever would be altogether *impossible*. I refer to the concept of *universality*. All concepts about nature which are gained by positive construction out of elements resulting from analysis, claim to be of *universal validity*; without that claim there could indeed be no science.

Of course this is no place for a lecture on methodology, and it therefore must suffice to make one remark with special regard to our purpose, which we should like to emphasise. Our concept of the harmonious-equipotential system--say rather, our concept of the prospective potency itself--presumes the understanding that indeed *all* blastomeres and *all* stems of *Tubularia*, including those upon which we have *not* carried out our experiments, will behave like those we have experimented with; and those concepts also presume that a certain germ of Echinus, *A*, the blastomeres of which were not separated, would have given two whole larvae, if separation had taken place, while another germ, *B*, which actually gave us two larvae after separation, would only have given one without it. Without this presumption the concept of “potency” is meaningless, and, indeed, every assumption of a “faculty” or a “possibility” would be meaningless in the whole area of science.

But this presumption can never be proved; it can only be postulated. It therefore is only with this postulate that our first proof of vitalism holds; but this restriction applies to *every* law of nature.

I cannot force you to agree with this postulate: but if you decline you are practically saying that there exists a sort of pre-established harmony between the scientific object and the scientist, the scientist always getting into his hands such objects only as have been predestinated from the very beginning to develop two larvae instead of one, and so on.

Of course, if that is so, no proof of natural laws is possible at all; but nature under such views would seem to be really dæmonic.

And so, I hope, you will grant me the postulate of the universality of scientific concepts--the only “hypothesis” which we need for our argument.

4. ON CERTAIN OTHER FEATURES OF MORPHOGENESIS ADVOCATING ITS AUTONOMY

Our next studies on the physiology of form will be devoted in the first place to some additional remarks about our harmonious-equipotential systems themselves, and about some other kinds of morphogenetic “systems” which show a certain sort of relationship with them. For it is of the greatest importance that we should become as familiar as possible with all those facts in the physiology of form upon the analysis of which are to be based almost all of the future theories that we shall have to develop in biology proper and philosophical. Our discussions, so far as they relate to questions of actual fact, will contain only one other topic of the same importance.

But though it is designed to complete and to deepen our analysis, the present considerations may yet be said to mark a point of rest in the whole of our discussions: we have followed one single line of argumentation from the beginning until now; this line or this stream of thought, as you might call it, is now to break into different branches for a while, as if it had entered from a rocky defile into a plain. It seems to me that such a short rest will be not unconducive to a right understanding of all we have made out; and such a full and real conceiving again, such a realising of our problems of morphogenesis and their solutions, will be the best preparation for the philosophical part of these lectures.

HARMONIOUS-EQUIPOTENTIAL SYSTEMS FORMED BY WANDERING CELLS

All of the harmonious-equipotential systems which we have studied so far were the bases of histological differentiation; that is to say, the processes of their differentiation consisted in specifically localised elements of theirs becoming different *in situ*. Now we know at least one type of systems which also may be called harmonious-equipotential, but the differentiation of which does not simply relate to elements at a fixed place. An additional phenomenon enters here into the sphere of the others. The elements not only become different where they are, but a specific changing of locality, a specific kind of wandering, goes hand-in-hand with differences relating to the prospective value to be attained. I am speaking of the formation of the larval skeleton of our well-known Echinus. We know that the mesenchyme cells, which have left the blastoderm and are arranged in a sort of ring of bilateral structure, are the starting-point of this skeleton: it indeed originates in a sort of secretive process on the part of the cells; the cells are moving about and are secreting carbonate of lime during their wandering. The experiments now have shown, as we know, that a whole, though smaller, skeleton may also be formed, if only a half or a quarter of the mesenchyme cells are present, as happens to be the case in all experiments with isolated blastomeres of the two or four-cell stage of cleavage. It is clear that in these cases the performance of each single cell must be different from what it is in the normal case, and that the same sort of differences in the morphogenetic performances appears again, if the two- and the four-cell stage are compared with each other. And there are still some other phenomena showing the possibility of different performances being carried out by the individual cells. Peter has shown that the number of mesenchyme cells may vary enormously under certain conditions; but, in spite of that, the skeleton always will be complete. It may be said that this line of research is only of a relative value to our own questions, as, of course, variability relates to different individuals: but it seems to me that it adds a very good supplementary instance to what the experiment on the individual itself has established.

We should only be repeating ourselves if we were to analyse again what happens here as the expression of the harmonious-equipotentiality itself. But indeed there occurs something new in this instance: the single mesenchyme cell not only has to perform in each case that single act of specific secretion which the case requires, but it also has to wander to the right place in order to perform it; there must be some order, not only about the acts of secretion after wandering, but also in the migrations themselves. If undisturbed ontogeny alone were possible, and if therefore a theory like that of Weismann were in place, we might say perhaps that each mesenchyme-cell is specified not only as to its performance in secretion, but also with regard to its chemotactical irritability, the latter being typically localised, so that its effect becomes typical, thanks to the typical arrangement of all the cells with respect to each other. But that is certainly not the case. Now, you may ask yourselves if you could imagine any sort of a machine, which consists of many parts, but not even of an absolutely fixed number, all of which are equal in their faculties, but all of which in each single case, in spite of their potential equality, not only produce together a certain typical totality, but also arrange themselves typically in *order* to produce this totality. We *are* indeed familiar with certain occurrences in nature where such curious facts are observed, but I doubt if you would speak of “machines” in these cases. The mesenchyme-cells, in fact, behave just as a number of workmen would do who are to construct, say, a bridge. All of them *can* do every single act, all of them also *can* assume every single position: the result always is to be a perfect bridge; and it is to be a perfect bridge even if some of the workmen become sick or are killed by an accident. The “prospective values” of the single workman change in such a case.

I well know that it is only an analogy which I am offering to you. The mesenchyme-cells have not “learned,” have no “experience.” All that is to occupy us next summer. But in spite of it, there is truth in the analogy; and perhaps you will prefer it to the merely abstract consideration.

ON CERTAIN COMBINED TYPES OF MORPHOGENETIC SYSTEMS

For the sake of completeness it may be remarked, only by the way, that the type of the proper harmonious-equipotential system may go hand in hand with another type of “systems” which play a part in morphogenesis; a type which we have shortly mentioned already and which will be studied fully a few chapters later. We know that there are equipotential systems with complex potencies: that is to say, systems which may produce a whole organism equally well from any one of their elements; we know the cambium of Phanerogams to be such a system. Now it is easily understood that the germ of our Echinus, say in the stage of two or four or eight cleavage cells, is not only an harmonious-equipotential system, but a complex-equipotential system too. Not only may there arise a whole organism out of 2/4 or 3/4 or 3/8, 4/8, 5/8, 6/8, 7/8 of its elements, in which cases the harmonious rôle of the single element with regard to its single performance in a totality is variable, but there may also arise four whole single larvae out of the four cells of the four-cell stage, or eight single whole larvae out of the eight-cell stage.[67] In these cases, of course, each of the four or eight elements has performed not a part of the totality, changing with its “position,” but the totality itself. With respect to these possible performances the “systems” present in the four or eight-cell stages of cleavage must be called complex-equipotential ones.

[67] The eight larvae would be incomplete in some respect, but not with regard to symmetry. They would be “whole” ones, only showing certain defects in their organisation. See page 65 note 1, and page 73.

We propose to give the name of *mixed-equipotential systems* to all those equipotential systems which, at the same time, may be regarded as belonging to the harmonious or to the complex type. It is not only among cleavage-stages that they are to be found; you may also find them very clearly exhibited in our ascidian *Clavellina* for instance. We know already that the branchial apparatus of this form is typically harmonious-equipotential, but it is complex-equipotential too, for it also may regenerate what is wanting in the proper way, by a budding from the wound; and the same is true of many other cases, the flatworm *Planaria* for instance.

Another type of systems, which might be said to be of a higher degree, is exhibited in some very strange phenomena of regeneration. It was first shown most clearly by some experiments of Godlewski’s that a whole tail may be regenerated from a wound inflicted on the body of a newt, even if this wound involves section of only a portion of the body-diameter. Section of the whole of the body-diameter of course would cause the formation of the whole tail also; but it was found that even an incomplete cross-section of the body is capable of performing the whole on a smaller scale. The series of possible cross-sections which are all capable of regeneration would have to be called a system of the complex type in this case; but, now we learn that every *single* cross-section is of the harmonious type, we must speak of *complex-harmonious systems*. What we have described is not the only instance of our new type of morphogenetic systems. Some other instances had been discovered a few years earlier, though nobody had pointed out their true significance. In the flatworm *Planaria* a partial cross-section is also capable of forming a whole structure, say a head, and all cases of so-called “super-regeneration” after the infliction of a complicated wound probably belong here also.