Chapter IX: The Prosomatic Segments of Ammocoetes

The prosomatic region in Ammocoetes--The suctorial apparatus of the
adult Petromyzon--Its origin in Ammocoetes--Its derivation from
appendages--The segment of the lower lip or the metastomal segment--
The tentacular segments--The tubular muscles--Their segmental
arrangement--Their peculiar innervation--Their correspondence with
the system of veno-pericardial muscles in Limulus--The old mouth
or palæostoma--The pituitary gland--Its comparison with the coxal
gland of Limulus--Summary 286