CHAPTER IX. The Prosomatic Segments of Ammocoetes

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