Chapter XIV: Part 14

For the next 20 years little was done, and then began the evolution of the high "ordinary" bicycle with a large driving wheel in front and a small trailing one behind. About 1865 Pierre Lallement in Paris constructed a bicycle in which the front wheel was driven by pedals and cranks attached directly to its axle, but it is doubtful whether the origin of this idea must be attributed to him or to Ernest Michaux, the son of his employer, who was a carriage repairer. Lallement took his machine to the United States, and in 1866 was granted a patent which had an important influence on the subsequent course of the cycle industry in that country. This machine, consisting of a wooden frame supported on two wooden wheels (fig. 3), soon became popular in England, as well as in France and America, and came to be called bicycle (or bysicle) by those who took it seriously and "boneshaker" by those who did not. Improvements quickly followed, chiefly in England, for in America the popularity of the machine was short-lived, and in France the industry was checked by the Franco-German war. Rubber tires, in place of iron ones, appeared in 1868, and in two or three years were made very large, 2 in. or more in width. Suspension wheels, with wire spokes in tension, were seen at the Crystal Palace, London, on the "Phantom" (fig. 4) of W. F. Reynolds and J. A. Mays in 1869, and early in the same year the manufacture of bicycles, at first for export to France, was begun in England by the Coventry Sewing Machine Company, till then makers of sewing machines. There was a rapid growth in the size of the front wheel, which in the boneshaker normally measured 36 or 38 in. in diameter, with a corresponding shrinkage in the rear wheel (fig. 5), until by 1874, the date of the invention of the tangent wheel by J. K. Starley 54-in. wheels were being made. The high bicycle was now fairly established in form, and the changes made in the subsequent 10 or 15 years during which it retained its supremacy were chiefly in the details of construction, such as the adoption of steel tubing for the frames, the use of hollow rims in the wheels and the application first of cone and then of ball bearings to points of friction. The weight of a 54-in. bicycle, which in 1874-1875 exceeded 50 or even 60 lb., was thus reduced to well under 40 lb. in machines intended for use on ordinary roads, and to not much over 20 lb. in the case of racers.

The high "ordinary" bicycle (fig. 6) gave unquestionable pleasure to many riders, and very fast times were made with it both on the road and on the racing path. In 1882 H. L. Cortis rode 20 m. 300 yds. in one hour, and in April 1884 Thomas Stevens started from San Francisco to ride round the world, a feat which he accomplished in December 1886. But it had various disadvantages. The vibration set up by the small back wheel was very trying, and in spite of the size of the front one the rider had to move his pedals at an uncomfortably rapid rate if he wished to maintain a good speed. Moreover his seat was placed in such a position that he was liable to be pitched over the handlebar if his wheel encountered a comparatively small obstacle. Attempts were made to remedy these inconveniences in various ways. From the early 'eighties much attention was devoted to tricycles, and these were produced in innumerable designs, whether for a single rider, or for two in the form of "sociables," in which the riders sat side by side, or of "tandems," in which one sat behind the other. But their weight, and consequently the exertion of propelling them, was necessarily greater than in the case of the bicycle, and by the end of the decade, the demand for them had fallen off, though they are still made to a certain extent, chiefly for carrying purposes. The two-track dicycle (fig. 7), invented by E. C. F. Otto about 1879, in which the rider balanced himself between two equal wheels placed abreast, also failed to secure lasting success.

The improvement of the high bicycle was attempted in two directions. On the one hand it was modified by placing the rider farther back, his position "over his work" being ensured by arranging the pedals immediately below him and connecting them to the front wheel, which was usually reduced in size, by levers and cranks or by chain-gearing, often with a multiplying action. On the other, the rear wheel was enlarged and made the driving wheel. The "'Xtraordinary" (fig. 8), "Facile" (fig. 9) and "Kangaroo" were examples of the former kind, which were often spoken of as "dwarf-safeties"; but though a good many of them were used about 1880 and following years, both they and the "ordinary" bicycle ultimately disappeared before machines of the second kind, which developed into the modern rear-driven safety. There are numerous claimants for the invention--or rather the reinvention--of this type, but it appears that the credit for its practical and commercial introduction in substantially its present form is due to J. K. Starley in England. His "Rover" (fig. 10), brought out late in 1885, had two nearly equal wheels, the driving wheel 30 in. in diameter and the steering 32 in., and the rider sat so far back that he could not be thrown forward over the handles. The motion imparted by the pedals to a sprocket wheel mounted between the wheels was transmitted by an endless chain to the rear wheel, and by sufficiently increasing the size of this sprocket wheel the machine could be made to travel as far or farther than the "ordinary" for each complete revolution of the pedals. From about 1890 the "safety" monopolized the field. At first it was fitted with the narrow rubber tires customary at the time, but these gave way to pneumatic tires, invented in 1888 by J. B. Dunlop, a veterinary surgeon of Belfast, whose idea, however, had been anticipated in the English patent taken out by R. W. Thomson in 1845. The result was a great gain in comfort, due to reduction of vibration, and a remarkable increase of speed or, alternatively, decrease of exertion. Subsequent progress was mainly in the details of design and manufacture, tending to secure lightness combined with adequate strength, and such was the success attained, by the application of scientific principles and of improved methods and materials to the construction of the frames and other parts, that while the weight of the original "Rover" was about 50 lb. that of its successors 20 years later with 28-in. wheels was reduced by 35 or 45%, or even 60% in the case of racing machines. The beginning of the 20th century saw the introduction of two innovations: one was the "free-wheel," a device which allows the driving wheel to rotate independently of the chain and pedals, so that the rider, controlling his speed with powerful brakes, can "coast" down a hill using the stationary pedals as foot-rests; and the other was the motor-cycle, in which a petrol-engine relieves him, except at starting, from all personal exertion, though at the cost of considerable vibration. A third contrivance, which, however, was an idea of considerably older date, also began to find favour about the same period in the shape of two-speed and three-speed gears, enabling the rider at will to alter the ratio between the speed of revolution of his pedals and of his driving wheel, and thereby accommodate himself to the varying gradients of the road he is traversing (see also BICYCLE, TRICYCLE and TIRE).

The safety bicycle, with pneumatic tires, rendered cycling universally popular, not merely as a pastime but as a convenient means of locomotion for everyday use. Made with a drop-frame, it also enabled women to cycle without being confined to a heavy tricycle or compelled to assume "rational dress." In consequence there was an enormous expansion in the cycle industry. In England the demand for machines had become so great by 1895 that the makers were unable to cope with it. Numbers of new factories were started, small shops grew into large companies, and the capital invested advanced by millions of pounds. The makers who had devoted their mechanical skill to perfecting the methods of cycle-construction were swallowed up by company promoters and adventurers, bent simply upon filling their own pockets. The march of mechanical invention and improvement was arrested, and machines, instead of being built by mechanics proud of their work, in many cases were merely put together in the shortest possible time and in a few standard patterns. For these the world clamoured, and for a year they could not be produced fast enough. Then the demand fell off, the British market became over-stocked, and as the British makers declined to consider the wants of foreign customers, their store-rooms remained crowded with machines that could not be sold. Speculative finance, such as was exemplified in 1896 by the flotation for L5,000,000 of the Dunlop tire company, which had been started in 1889 with a capital of L25,000, had its natural effects. There ensued widespread and continuing disorganization of the trade, which had to be met by extensive reconstructions of over-capitalized companies. English makers too had lost the commanding international position they once enjoyed, when they supplied almost the entire demand for bicycles in many parts of the world, including the United States. In America the manufacture of bicycles was not begun until about 1878, when it was introduced by A. A. Pope (1843-1909), and even by 1890 the value of the products barely exceeded 2(1/2) million dollars, while for several years later much of the steel tubing required for bicycle manufacture continued to be imported from Great Britain. The industry, however, thanks to automatic machinery and perfect organization, grew rapidly, and in 1900 the value of its products was nearly 32 million dollars. In the two years 1897 and 1898 the exports of cycles and cycle parts alone were worth nearly 14 million dollars, though they fell off in subsequent years, and English makers had to contend with an American invasion in addition to their domestic troubles. But the competition was short-lived. The American makers sent over machines with single tube tires and wooden rims which did not secure the approval of the British purchaser, and so they too lost their hold. In the opening years of the 20th century the industry in Great Britain gradually recovered itself. More attention was paid to the production of cheap machines which were sound and trustworthy, and sales were further stimulated by the introduction of systems of deferred payments. In 1905 about 600,000 machines were made in Great Britain, and 47,604 were exported, the total value of the home-market for cycles and their parts being about 3(1/2) millions sterling, and of the export trade about one million. In the same year the number of machines imported was only 2345.

Touring clubs.

Cycle tours were taken and cycle clubs established almost as soon as the cycle appeared, the Pickwick Bicycle Club in London, founded in 1870, being the oldest in the world. The organization of these clubs is chiefly of a social character, and a few possess well-appointed club-houses. To a great extent they have been superseded by the large touring organizations. The Cyclists' Touring Club, organized in 1878 as the Bicycle Touring Club, has members scattered through Europe, America and even the East. Many other countries possess national clubs, as for instance the League of American Wheelmen, founded in 1880, and the Touring Club de France, founded in 1895, of whose objects cycling is only one, though the chief. The aim of these national associations, which have formed an international touring league, is the promotion of cycle touring. To this end they publish roadbooks, maps and journals; they recommend hotels, with fixed tariffs, in their own and other countries; they appoint representatives to aid their members when touring; and they have succeeded in inducing most governments to allow their members to travel freely across frontiers without paying duty on their machines. In all countries they have erected warning-boards at dangerous places; in France the best route is suggested by a sign-post, and cyclists who meet with accidents in lonely places find repair outfits provided for their free use. Another important part of the work of these clubs, either directly or indirectly, is the improvement of the roads. France has done more for the cyclist than any other country, owing to the fact that she possesses the best roads, kept up to a certain extent by the cycle tax, whereby the cyclist acquires a certain official position and right; moreover cycles accompanied by their owners are conveyed without extra charge on the railways, and aid is given to the sport and pastime from public funds. In Belgium the cycle has worked a veritable revolution in the national life. The surface of the greater part of the country being loose and sandy, the roads have been paved, and this paving is so bad as to be impossible for light traffic. The cycle tax has consequently been devoted, first, to the construction of paths on which cyclists have equal rights with pedestrians, and secondly to the replacing of the paving by macadam. In this way alone cycling has proved of inestimable benefit to Belgium and Luxembourg. In the United States measures for securing good roads and side paths have been introduced in various states, mainly at the instigation first of cyclists and then of motorists, and in Great Britain the Roads Improvement Association has worked for the same end.

Racing.

Each country also possesses an organization for the government of cycle racing; and although these unions, one object of which--usually the main one--is the encouragement of cycle racing and cycle legislation, boast an enormous membership, their membership is often composed of clubs and not individuals. Among the most important are the National Cyclists' Union of England and the Union Velocipedique of France. These bodies are also bound together by the International Cyclists' Association, which is devoted mainly to the promotion of racing and legislation connected with it all over the world. The National Cyclists' Union, originally the Bicycle Union, which was the parent body of all, formed in February 1878, was the first to put up danger-boards, and also was early instrumental, alone and with the C.T.C., in framing or suggesting laws for the proper government and regulation of cycle traffic, notably in establishing its position as a vehicle in securing universal rights, in endeavouring, again in conjunction with the C.T.C., to increase facilities for the carriage of cycles on the railways, in securing the opening of parks, and in promoting many other equally praiseworthy objects. For a number of years, however, it has been more prominent as the ruling race-governing body. But cycle racing has fallen upon evil days. At one time cycle racing attracted a large number of spectators, but gradually it lost the public favour, or rather was ignored by the public because it became mainly an advertisement for cycle makers. The presence of the man, directly or indirectly, in the employ of, or aided by a maker, and the consequent mixing up of trade and sport, lowered racing not only in the public estimation, but in that of all genuine amateurs. There have always been a few amateurs who have raced for the love of the sport, but the greater number of prominent racing men have raced for the benefit of a firm, so much so that, at one time, an entire section of racing men were classed as "makers' amateurs." They did not confine themselves to the race track, but appropriated the public roads until they became a danger and a nuisance, and road-racing finally was abolished, though record rides, as they are called, are still indulged in, being winked at by the police and by the cycling authorities. The makers' amateurs at least rode to win and to make the best time possible. But the scandal was so great that a system of licensing riders was adopted by the N.C.U., and if this did not effectively kill the sport, the introduction of waiting races did. There probably is considerable skill in riding two-thirds of a race as slowly as possible, and only hurrying the last part of the last lap, but it does not amuse the public, who want to see a fast race as well as a close finish. The introduction of pacing by multicycles and motors next took from cycle racing what interest was left. A motor race, in which the machines are run at top speed, is more exciting than the spectacle of a motor being driven at a rate which the cyclist can follow with the protection of a wind-shield. In America this system of proving what cyclists can do with racing machines was carried so far that in 1899 a board track was laid down on the Long Island railway for about 2 m. between the metals, and a cyclist named Murphy, followed a train, and protected by enormous wind-shields, succeeded in covering a mile in less than a minute in the autumn of 1900. Other cyclists have devoted themselves, at the instigation of makers, to the riding of 100 m. a day every day for a year. It would be difficult to say what advantage there is in these trials and contests. They are not convincing records, and only prove that some people are willing to take great personal risks for the benefit of their employers. E. Hale, during 1899-1900, covered 32,496 m. in 313 days. For many years also long-distance races, mostly of six days' duration, have been promoted on covered tracks, and though condemned by all cycling organizations, they find a great deal of pecuniary support.

Military.

The cycle has also been taken up for military purposes. For this idea the British army is indebted to Colonel A. R. Savile, who in 1887 organized the first series of cycle manoevres in England. Since then military cycling has undergone a great development, not only in the country of its origin but in most others.

Literature.

Cycling has produced a literature of its own, both of the pastime and
of the trade. Owing to the enormous profits which, for several years,
were obtained by cycle makers, a trade press appeared which simply
lived by, and out of, its advertisers; and though each country has one
or more genuine trade journals, the large proportion of these sheets
have been worth, in a business aspect, as little practically as from a
literary standpoint. On the other hand a vast mass of practical and
unpractical, scientific and medical, historical and touring treatises
and records have appeared, but mostly of a rather ephemeral character.

CYCLOID (from Gr. [Greek: kuklos], circle, and [Greek: eidos], form), in geometry, the curve traced out by a point carried on a circle which rolls along a straight line. The name cycloid is now restricted to the curve described when the tracing-point is on the circumference of the circle; if the point is either within or without the circle the curves are generally termed _trochoids_, but they are also known as the _prolate_ and _curtate_ cycloids respectively. The cycloid is the simplest member of the class of curves known as roulettes.

No mention of the cycloid has been found in writings prior to the 15th century. Francis Schooten (_Commentary on Descartes_) assigns the invention of the curve to Rene Descartes and the first publication on this subject after Descartes to Marin Mersenne. Evangelista Torricelli, in the first regular dissertation on the cycloid (_De dimensione cycloidis_, an appendix to his _De dimensione parabolae_, 1644), states that his friend and tutor Galileo discovered the curve about 1599. John Wallis discussed both the history and properties of the curve in a tract _De cycloide_ published at Oxford in 1659. He there shows that the cycloid was investigated by Carolus Bovillus about 1500, and by Cardinal Cusanus (Nicolaus de Cusa) as early as 1451. Honore Fabri (_Synopsis geometrica_, 1669) treated of the curve and enumerated many theorems concerning it. Many other mathematicians have written on the cycloid--Blaise Pascal, W. G. Leibnitz, the Bernoullis, Roger Cotes and others--and so assiduously was it studied that it was sometimes named the "Helen of Geometers." The determination of the area was the subject of many investigations and much controversy. Galileo attempted the evaluation by weighing the curve against the generating circle; this rough method gave only an approximate value, viz., a little less than thrice the generating circle. Torricelli, by employing the "method of indivisibles," deduced that the area was exactly three times that of the generating circle; this result had been previously established in 1640 in France by G. P. de Roberval, but his investigation was unknown in Italy. Blaise Pascal determined the area of the section made by any line parallel to the base and the volumes and centres of gravity of the solids generated by revolving the curve about its axis and base. Before publishing his results he proposed these problems for public competition in 1658 under the assumed name of Amos Dettonville. John Wallis in England, and A. la Louere in France, accepted the challenge, but the former could only submit incorrect solutions, while the latter failed completely. Having established his priority, Pascal published his investigations, which occasioned a great sensation among his contemporaries, and Wallis was enabled to correct his methods. Sir Christopher Wren, the famous architect, determined the length of the arc and its centre of gravity, and Pierre Fermat deduced the surface of the spindle generated by its revolution. A famous period in the history of the cycloid is marked by a bitter controversy which sprang up between Descartes and Roberval. The evaluation of the area of the curve had made Roberval famous in France, but Descartes considered that the value of his investigation had been grossly exaggerated; he declared the problem to be of an elementary nature and submitted a short and simple solution. At the same time he challenged Roberval and Fermat to construct the tangent; Roberval failed but Fermat succeeded. This problem was solved independently by Vicenzo Viviani in Italy. The cartesian equation was first given by Wilhelm Gottfried Leibnitz (_Acta eruditorum_, 1686) in the form y = (2x - x^2)(1/2) + [int](2x - x^2)(1/2)dx. Among other early writers on the cycloid were Phillippe de Lahire (1640-1718) and Francois Nicole (1683-1758).

The mechanical properties of the cycloid were investigated by Christiaan Huygens, who proved the curve to be tautochronous. His enquiries into evolutes enabled him to prove that the evolute of a cycloid was an equal cycloid, and by utilizing this property he constructed the isochronal pendulum generally known as the _cycloidal pendulum_. In 1697 John Bernoulli proposed the famous problem of the _brachistochrone_ (see MECHANICS), and it was proved by Leibnitz, Newton and several others that the cycloid was the required curve.

The method by which the cycloid is generated shows that it consists of
an infinite number of cusps placed along the fixed line and separated
by a constant distance equal to the circumference of the rolling
circle. The name cycloid is usually restricted to the portion between
two consecutive cusps (fig. 1, curve a); the fixed line LM is termed
the base, and the line PQ which divides the curve symmetrically is the
_axis_. The co-ordinates of any point R on the cycloid are expressible
in the form x = a([theta] + sin [theta]); y = a(1 - cos [theta]),
where the co-ordinate axes are the tangent at the vertex O and the
axis of the curve, a is the radius of the generating circle, and
[theta] the angle R'CO, where RR' is parallel to LM and C is the
centre of the circle in its symmetric position. Eliminating [theta]
between these two relations the equation is obtained in the form x =
(2ay - y^2)(1/2) + a vers-^1 y/a. The clumsiness of the relation
renders it practically useless, and the two separate relations in
terms of a single parameter [theta] suffice for the deduction of most
of the properties of the curve. The length of any arc may be
determined by geometrical considerations or by the methods of the
integral calculus. When measured from the vertex the results may be
expressed in the forms s = 4a sin 1/2[theta] and s = [root](8ay); the
total length of the curve is 8a. The intrinsic equation is s = 4a sin
[psi], and the equation to the evolute is s = 4a cos [psi], which
proves the evolute to be a similar cycloid placed as in fig. 2, in
which the curve QOP is the evolute and QPR the original cycloid. The
radius of curvature at any point is readily deduced from the intrinsic
equation and has the value [rho] = 4 cos 1/2[theta], and is equal to
twice the normal which is 2a cos 1/2[theta].

The _trochoids_ were studied by Torricelli and F. van Schooten, and
more completely by John Wallis, who showed that they possessed
properties similar to those of the common cycloid. The cartesian
equation in terms similar to those used above is x = a[theta] + b sin
[theta]; y = a - b cos [theta], where a is the radius of the
generating circle and b the distance of the carried point from the
centre of the circle. If the point is without the circle, i.e. if a <
b, then the curve exhibits a succession of nodes or loops (fig. 1,
curve b); if within the circle, i.e. if a > b, the curve has the form
shown in fig. 1, curve c.

The _companion to the cycloid_ is a curve so named on account of its
similarity of construction, form and equation to the common cycloid.
It is generated as follows: Let ABC be a circle having AB for a
diameter. Draw any line DE perpendicular to AB and meeting the circle
in E, and take a point P on DE such that the line DP = arc BE; then
the locus of P is the companion to the cycloid. The curve is shown in
fig. 3. The cartesian equation, referred to the fixed diameter and the
tangent at B as axes may be expressed in the forms x = a[theta], y =
a(1 - cos [theta]) and y - a = a sin (x/a - 1/2[pi]); the latter form
shows that the locus is the harmonic curve.

For epi- and hypo-cycloids and epi- and hypo-trochoids see EPICYCLOID.

REFERENCES.--Geometrical constructions relating to the curves above
described are to be found in T. H. Eagles, _Constructive Geometry of
Plane Curves_. For the mechanical and analytical investigation,
reference may be made to articles MECHANICS and INFINITESIMAL
CALCULUS. A historical bibliography of these curves is given in
Brocard, _Notes de bibliographie des courbes geometriques_ (1897). See
also Moritz Cantor, _Geschichte der Mathematik_ (1894-1901).

CYCLOMETER (Gr. [Greek: kyklos], circle, and [Greek: metron], measure), an instrument used especially by cyclists to determine the distance they have traversed. In a common form a stud attached to one spoke of the wheel engages with a toothed pinion and moves it on one tooth at each revolution. The pinion is connected with a train of clockwork, the gearing of which bears such a ratio to the circumference of the wheel that the distance corresponding to the number of times it has revolved is shown on a dial in miles or other units.

CYCLONE (Gr. [Greek: kyklon], whirling, from [Greek: kyklos], a circle), an atmospheric system where the pressure is lowest at the centre. The winds in consequence tend to blow towards the centre, but being diverted according to Ferrel's law they rotate spirally inwards at the surface of the earth in a direction contrary to the movement of the hands of a watch in the northern hemisphere, and the reverse in the southern hemisphere. The whole system has a motion of translation, being usually carried forward with the great wind-drifts like eddies upon a swift stream. Thus their direction of movement over the British Islands is usually from S.W. to N.E., though they may remain stationary or move in other directions. The strength of the winds depends upon the atmospheric gradients. (See METEOROLOGY.)

CYCLOPEAN MASONRY (from the Cyclopes, the supposed builders of the walls of Mycenae), a term in architecture, used, in conjunction with Pelasgic, to define the rude polygonal construction employed by the Greeks and the Etruscans in the walls of their cities. In the earliest examples they consist only of huge masses of rock, of irregular shape, piled one on the other and trusting to their great size and weight for cohesion; sometimes smaller pieces of rock filled up the interstices. The walls and gates of Tiryns and Mycenae were thus constructed. Later, these blocks were rudely shaped to fit one another. It is not always possible to decide the period by the type of construction, as this depended on the material; where stratified rocks could be obtained, horizontal coursing might be adopted; in fact, there are instances in Greece, where a later wall of cyclopean construction has been built over one with horizontal courses.

CYCLOPES ([Greek: Kyklopes], the round-eyed, plural of Cyclops), a type of beings variously described in Greek mythology. In Homer they are gigantic cave-dwellers, cannibals having only one eye, living a pastoral life in the far west (Sicily), ignorant of law and order, fearing neither gods nor men. The most prominent among them was Polyphemus. In Hesiod (_Theogony_, 264) they are the three sons of Uranus and Gaea--Brontes, Steropes and Arges,--storm-gods belonging to the family of the Titans, who furnished Zeus with thunder and lightning out of gratitude for his having released them from Tartarus. They were slain by Apollo for having forged the thunderbolt with which Zeus slew Asclepius. Later legend transferred their abode to Mt Aetna, the Lipari islands or Lemnos, where they assisted Hephaestus at his forge. A third class of Cyclopes are the builders of the so-called "Cyclopean" walls of Mycenae and Tiryns, giants with arms in their belly, who were said to have been brought by Proetus from Lycia to Argos, his original home (Pausanias ii. 16. 5; 25. 8). Like the Curetes and Telchines they are mythical types of prehistoric workmen and architects, and as such the objects of worship.

The standard work on these and similar mythological characters is M.
Mayer, _Die Giganten und Titanen_ (1887); see also A. Boltz, _Die
Kyklopen_ (1885), who endeavours to show that they were an historical
people; W. Mannhardt, _Wald- und Feldkulte_ (1904); J. E. Harrison,
_Myths of the Odyssey_ (1882); and article in Roscher's _Lexikon der
Mythologie_ (bibliography).

CYCLOSTOMATA, or MARSIPOBRANCHII, a group of fishes including the ordinary lampreys and hagfish, and so called from the wide permanently gaping mouth which is without the hinged jaws characteristic of other vertebrates (GNATHOSTOMATA). The class Cyclostomata consists of two orders, the Myxinoids (or Hyperotreti) and the Petromyzontes (or Hyperoartii), which, while showing sufficient resemblance in structure to warrant their inclusion in the same class, are yet marked off by such deep-seated differences as to indicate that they commenced to diverge from one another far back in evolutionary time. The order Myxinoids includes the hagfish (_Myxine_), common off the eastern, and occurring also, though less commonly, off the western coasts of the north Atlantic, and the genus _Bdellostoma_ (also known as _Homea_, _Eptatretus_, in part--_Polistotrema_), including the "borers" of the western American coast, New Zealand and the Cape of Good Hope. The order Petromyzontes includes the widely distributed lampreys. The original genus _Petromyzon_ (which it is now customary to subdivide into a number of genera) includes the large sea lamprey (_P. marinus_) of the north Atlantic coasts and the two fresh-water lampreys of European streams (_P. fluviatilis_ and _P. planeri_, the latter of which is possibly only a small-sized variety of the former species). In North America nine or ten species of lampreys are known to occur, descriptions of which are given by Jordan and Evermann (1). In the southern hemisphere occur the two genera Mordacia (Chile, Tasmania) and _Geotria_ (Chile, Australia, New Zealand) (2).

The Cyclostomes are remarkable among vertebrates in that they are semiparasitic in habit. The lampreys--except some of the small fresh-water forms--attach themselves to other fishes by their suctorial mouth and proceed to rasp off the flesh by means of the horny teeth carried by the highly-developed tongue. The Myxinoids have gone a step further and actually bore their way right into the body of their prey, devouring all the soft parts and leaving the skin behind as a mere shell, empty but for the bones. Where the hagfish or borers are abundant, as in certain localities off the east coast of Scotland and off the west coast of California, they may do great damage to fisheries from their habit of attacking fishes which are in difficulties through being caught by a hook or in a net; the fish when drawn up being frequently completely deprived of their flesh.

The Myxinoids retain the ancestral marine habitat, but the lampreys have sought refuge from the struggle for existence by taking to fresh water to a less or greater extent. Such a form as _Petromyzon marinus_ or _Entosphenus tridentatus_ of the west coast of America is what is known as anadromous in habit, i.e. it takes refuge in fresh water during the breeding season, ascending rivers like the salmon for the purpose of spawning. Certain species of lampreys, on the other hand, have completely deserted the sea and spend their whole lives in fresh-water streams or lakes. The lake lampreys show a reminiscence of their ancestral migratory habits in leaving lakes and ascending streams in order to deposit their spawn.

_Anatomy._--In structural features, the Cyclostomes show a curious mixture of features which must be looked on as primitive with others which are indicative of high specialization for their peculiar mode of life. In general appearance they are "eel-like": they are elongated in shape and adapted for swimming in eel fashion, i.e. the body is propelled forward by the backward passage along it of waves of lateral flexure. There are, however, certain conspicuous differences which at once serve to distinguish a Cyclostome from any other fishes of eel-like shape:--(1) the circular permanently open mouth, (2) the absence of all trace of paired limbs, (3) the absence of paired external nasal openings, and (4) the presence on the roof or at the tip of the head of a conspicuous median opening--the pituitary opening.

It will be convenient, in describing the structural features of the
group, to take as a basis for the description the marine lamprey,
_Petromyzon marinus_. A marine lamprey is an eel-like creature 70 to
75 cm. in length. At the anterior end and situated somewhat ventrally
is the circular widely gaping mouth or buccal cavity, its lining
studded with sharply pointed thorn-like "teeth" and its edge fringed
with numerous sensory papillae. On the dorsal side of the head is the
conspicuous circular pituitary opening with prominent lips, while on
the sides are seen the eyes, and behind these a row of somewhat
rounded branchial openings or gill-clefts. At about the beginning of
the posterior fourth of the body, and in the midventral line, is the
anal opening, and immediately behind it is the prominent papilla
carrying the opening of the urogenital sinus. The hinder portion of
the body, in accordance with its function in locomotion, is flattened
from side to side, while its surface is increased by the development
of a median fin fold, divided, except in early stages of development,
into three portions, known as the first and second dorsal fins and the
caudal fin. The last mentioned is of the primitive protocercal type.
The whole surface of the body--which shows a conspicuous dark
marbling, especially dorsally, on a light ground--is covered with
highly glandular epidermis. An important feature is the complete
absence of all trace of the calcified placoid plates which are so
characteristic of the Elasmobranchii.

The Myxinoids differ from the lampreys in regard to several of the
above-mentioned characters. The edges of the mouth carry tentacle-like
barbels. The pituitary opening is close to the anterior edge of the
mouth opening instead of being right up on the dorsal side of the
head. The eyes are invisible, being greatly reduced and sunk far below
the surface, and in _Myxine_, though not in _Bdellostoma_, the row of
gill openings is represented by a single opening on each side nearly
in the midventral line and situated at about the end of the first
quarter of the body length. Ventrally the Myxinoid possesses on each
side of the body a row of remarkable epidermal glands which can
produce at will enormous quantities of glutinous slime. This
secretion, which, no doubt, is of much value as a protection from
attack, is composed of very fine threads, formed by the conversion of
the protoplasm of certain cells of the epidermal glands ("thread
cells") into an extremely fine, tightly coiled filament, which becomes
unwound when discharged to the exterior.

FIG. 1.--The Marine Lamprey (_Petromyzon marinus_, L.).]

_Pituitary Tube._--A remarkable peculiarity of the Cyclostomes lies in
the fact that the pituitary ingrowth of ectoderm does not, as in other
forms, become involved in the inpushing of ectoderm which forms the
buccal cavity. On the contrary, it lies outside the edge of the
stomodaeum, and in the case of the lampreys active growth takes place
in the tissue between the pituitary and stomodaeal ingrowths, so that
the two openings come to be widely separated, the pituitary opening
being pushed back on to the dorsal side of the head. The pituitary
opening remains patent throughout life, as is the case with
Crossopterygians alone amongst Gnathostomata. In _Myxine_ a further
remarkable peculiarity in regard to the hypophysis, probably adaptive
in nature, occurs, inasmuch as the pituitary invagination develops an
opening at its posterior end into the pharynx.

_Nervous System._--The anterior end of the nervous tube is enlarged
and differentiated to form a brain as in other Vertebrates, but this
brain in the lampreys at least shows remarkably primitive features.
The enlargement as compared with the spinal cord is seen to be
comparatively slight: the brain is much elongated, and its various
regions lie in a straight line one behind the other: the roof of the
brain retains to a great extent the primitive epithelial condition. On
each side anteriorly there is present a comparatively large olfactory
lobe, and this is continued posteriorly into a small cerebral
hemisphere.

The lampreys are amongst those vertebrates in which there is an
eye-like apparatus (3) connected with the roof of the
thalamencephalon. There grow out from the roof of the thalamencephalon
two processes, a posterior (the pineal process), and an anterior (the
parapineal process). The pineal process grows forwards so as to
overlie the parapineal process. Each of these projections from the
roof of the thalamencephalon dilates to form a vesicle, and each
vesicle shows certain eye-like characteristics, its deep wall forming
a "retina" and its superficial wall being clear and translucent
("pellucida"). The retinal cells are packed in the case of the pineal
organ with opaque white pigment: similar pigment occurs in smaller
quantity in the parapineal organ. Definite sensory cells are also
present with rod-like structures projecting into the lumen of the
vesicle. Nerve fibres have been traced--from the pineal organ into the
posterior commissure and possibly into the right habenular ganglion.
As regards other parts of the brain, the chief point to note is that
the cerebellum is in a most rudimentary condition, forming merely a
slight transverse thickening of the hind-brain roof at its anterior
end. In Myxinoids the brain is much larger as compared with the spinal
cord, and it differs from that of the lampreys by being relatively
much shorter in an anteroposterior direction. A remarkable negative
feature lies in the complete absence of the pineal and parapineal
organs so conspicuous in the lampreys. The olfactory organ of
Cyclostomes is remarkable for two special characteristics, firstly,
that the two olfactory organs of other vertebrates are here
represented by a single median structure, and secondly, that the
olfactory organ becomes sunk down beneath the surface through becoming
involved in the ectodermal ingrowth which forms the pituitary tube. As
a further consequence in the case of the lampreys the olfactory organ
becomes transported to the roof of the head along with the pituitary
opening, which latter functions as an external nostril. That the
unpaired olfactory organ of existing Cyclostomes has passed through,
in their ancestors, a paired condition such as exists in other
vertebrates, is indicated by the fact that it retains a pair of
olfactory nerves.

The eyes in adult lampreys are of moderate size, while in the
Myxinoids they are greatly reduced--sunk beneath the skin
(_Bdellostoma_) or even in amongst the muscles of the head (_Myxine_).
The lens is completely absent, also the ocular muscles. The otocyst or
auditory organ is unique amongst craniate vertebrates in regard to the
semicircular canals. In the lampreys there are only two instead of the
normal three, while the Myxinoids have only one.

_Alimentary Canal._--The widely gaping buccal funnel is
morphologically an inpushing of the outer skin, i.e. it is stomodaeal
in nature. The thorn-like teeth which stud its lining are formed
simply by cornification of the epidermal cells (4) like the
provisional horny teeth of a tadpole, and are not homologous with the
true teeth of ordinary vertebrates. As to whether they represent the
remnant of a once present system of epidermal scales, which may have
preceded the coating of placoid elements in the evolution of the
vertebrate, there is no evidence.

FIG. 2.--Median longitudinal section through anterior end of
_Petromyzon_.

a.v.o, Atrio-ventricular opening.
br, Brain.
br.o, Internal opening of gill sac.
d.a, Dorsal aorta.
d.c, Ductus cuvieri.
h.v, Hepatic vein.
i.j.v, Inferior jugular vein.
N, Notochord.
oes, Oesophagus.
olf, Olfactory organ.
pc, Pericardium.
p.c.v, Left posterior cardinal vein.
pit, Pituitary tube.
V, Ventricle.
v, Velum.]

The pharyngeal region, closely associated with the respiratory
function, possesses, on each side, a series of gill-sacs (six in
_Myxine_: seven in _Petromyzon_, besides an anterior one which is laid
down in the embryo but disappears later: up to as many as fourteen in
_Bdellostoma_) opening on the one hand to the pharynx and on the other
to the exterior. In _Bdellostoma_ and in the larva of _Petromyzon_ the
gill-sacs open directly from the pharynx to the exterior, but in the
adult lamprey and in _Myxine_ the original relations are modified. In
_Myxine_, the external openings of the gill-sacs have migrated
backwards along the side of the body and become coincident at a point
slightly posterior to the last sac. It follows from this that each sac
is connected with the common aperture by a tube, longest in the case
of the first sac, shortest in the case of the last. In the adult
lamprey a different modification is found. Here the dorsal portion of
the pharynx has become nipped off as a narrow tube which functions as
an oesophagus from the larger ventral portion, which forms an
elongated saccular structure ending blindly at its hinder end and
having in its lateral wall the internal openings of the gill-sacs.

_Breathing._--The inspiratory current passes inwards by the mouth
opening in the larval lamprey, by the pituitary tube in _Myxine_,
while in the adult lamprey both expiration and inspiration takes place
through the external gill-openings. In the case of the lampreys the
elastic skeleton of the branchial region (see below) plays an
important part in respiration. The branchial region shows rhythmic
contraction through the agency of the transverse muscles--and
expansion, through the elasticity of the branchial skeleton--in the
adult lamprey. These rhythmic movements of the branchial region cause
successive inflow and outflow through the branchial openings. In the
larva, on the other hand, the respiratory current always passes in one
direction--backwards. This is helped by the presence of a velar fold
at the front end of the pharynx, which acts as a valve opening only
backwards, and to the presence of membranous flaps projecting back
from the anterior border of each gill-opening and acting as valves
which open only outwards.

Behind the pharynx comes the truly digestive part of the alimentary
canal in the form of a straight tube showing little differentiation
into special regions. The lining of the intestine is increased in area
by an inwardly projecting fold, which is compared by some
morphologists with the spiral valve of certain other groups. In the
mature river lamprey the digestive tract becomes in great part
degenerate.

_Coelomic Organs._--The chief point of interest about the
splanchnocoele or perivisceral cavity is that in the Myxinoids the
adult shows a persistent embryonic condition in that the pericardiac
portion never becomes isolated from the main body cavity.

The renal organs are of special interest in the Myxinoids from their
very simple character. The kidney duct is seen running along the roof
of the coelom on either side. Into the duct open short segmentally
arranged tubes, each possessing at its closed rounded extremity a
Malpighian body. Each of these short tubes is morphologically a
nephric tubule, which, however, in correlation with its shortness, is
without the turns and twists so characteristic of such tubules
generally. A further consequence of the short simple character of the
tubules is that they are quite separate from one another, instead of
being massed together to form a compact gland such as the kidney is
elsewhere. In _Petromyzon_ the kidney has the ordinary compact form,
and here also the Malpighian bodies are shut off from the
splanchnocoele.

The ovary or testis is a large unpaired structure hanging from the
dorsal wall of the splanchnocoele and shedding its products into it;
from the coelomic space the genital products pass into the urogenital
sinus--formed by the fusion of the kidney ducts at their hinder
ends--through a small opening, one at each side. This opening, which
leads directly from coelom into urogenital sinus, is known as the
genital pore. Its morphological significance is doubtful.

_Skeleton._--The vertebral column of the lamprey is represented by a
persistent notochord surrounded by a thick sheath, which shows no
signs of invasion by cartilage cells or of segmentation. Resting on
the sheath are paired dorsal arch elements, more numerous than the
neuromuscular segments. In the tail region these are united into a
continuous band of cartilage on each side: similar cartilaginous bands
represent the ventral arch elements of the tail region. The skeleton
of the head region consists of a cartilaginous cranium, into the
formation of which enter typical parachordal and trabecular elements,
together with olfactory and auditory capsules. In addition to these,
there are a number of other cartilaginous pieces present in the head
region, the homologies of which are doubtful.

_Branchial Basket._--One of the most characteristic features of the
skeleton of the lamprey is the remarkable cartilaginous "branchial
basket," which supports the gill region. In an adult river lamprey the
basketwork consists on each side of a series of eight vertical
half-hoops of cartilage. The hoops of each side are connected together
dorsally by a pair of longitudinal bars, lying ventral to the
notochord, and ventrally by a similar pair of rods which are fused in
the middle line. Slender cartilaginous projections arise from the
anterior and posterior sides of the hoops, and certain of these
meeting at their ends form additional longitudinal bars connecting
together successive hoops. Connected with the basketwork posteriorly
is a remarkable cup-shaped cartilage, which supports the hind wall of
the pericardium. The series of cartilaginous half-hoops naturally
suggest the half-hoops of cartilage which form the skeleton of the
visceral arches in the Gnathostomata. They are, however, more
superficial in position, and this has led many to doubt their actual
homology with the cartilaginous visceral arches. Taking into account,
however, our present knowledge of the development of the two sets of
structures, it seems on the whole probable that a true homology exists
and that the branchial basket of the lamprey represents merely a set
of visceral arches modified in accordance with the peculiar breathing
methods of the creature. In the Myxinoids the branchial basket is
reduced to a few vestigial masses of cartilage.

_Vascular System._--The heart (5) of the lamprey consists of an atrium
and a single ventricle, the atrium on the left, the ventricle on the
right. Into the atrium, on its right side, and behind the
atrio-ventricular opening, there opens a nearly vertical chamber
usually termed the sinus venosus (see below), the opening guarded by a
pair of vertically placed valves. The ventricle passes anteriorly into
what is clearly the homologue of the conus arteriosus of other forms.
In its interior are present a pair of laterally placed longitudinal
ridges similar to the ridges which occur in other forms in the conus.
The opening from ventricle into conus is guarded by a pair of
laterally placed pocket valves situated just within the boundary of
the ventricle.

The arterial system is of the ordinary piscine type. From the heart
there passes forwards a ventral aorta, split into two separate vessels
in its anterior half, and giving off on each side a series of efferent
vessels to the gill-sacs, one passing between each two gill-sacs and
an additional one to the front wall of the front sac and to the
posterior wall of the last. The blood is collected from the walls of
the gill-sacs by a series of efferent vessels which open into the
dorsal aorta. It is to be noted that the dorsal aorta retains the
probably primitive unpaired condition, except for a very short extent
at its anterior end, where it is split so as to form two short aortic
roots.

_Venous System._--The main venous channels are like those in other
fishes, though their connexion with the heart becomes modified in the
adult. The two posterior cardinals--with their continuations forwards,
the anterior cardinals--approach the median plane and undergo fusion
in the region of their opening into the two ductus Cuvieri. The left
ductus Cuvieri then atrophies so that all the blood from the cardinals
reaches the heart by way of the originally right ductus Cuvieri. It
is this right ductus Cuvieri which forms the dorsal part of what is
usually termed the sinus venosus. The inferior jugular veins which
return the blood from the ventral side of the head also become
replaced in the adult by a median unpaired vein which opens
posteriorly into the sinus venosus by what probably represents the
hinder end of the original right inferior jugular. It is interesting
to note that in _Polypterus_, one of the Crossopterygian ganoids,
there is a somewhat similar asymmetrical condition of inferior
jugulars and ductus Cuvieri.

_Oviposition of Lamprey_ (6).--The lamprey chooses as spawning ground
a part of the stream with fairly rapid current and where the bottom is
composed of sand with scattered stones. By means of the suctorial
mouth, stones are removed from more or less circular area so as to
form a shallow excavation. The male and female frequently work
together at the task of preparing the nest. When oviposition is about
to take place, the male may be seen to suddenly attach himself to the
dorsal surface of the head of the female which holds on to one of the
stones at the upper margin of the nest. The urogenital opening of the
male, with its specially prominent papilla, is approximated to that of
the female, and with a peculiar quivering movement the eggs and sperms
are emitted synchronously amidst clouds of sand stirred up by the
movements of the tail. The eggs fertilized thus at the moment of exit
are very sticky from their coating of albumen, and become weighted
down by adherent grains of sand.