PROCEEDINGS OF SOCIETIES. 201 



these vessels^ and they most certainly represent the contractile 

 non-ciliated portion of the water-vascular system. Deeper 

 than the dermis and its thickenings lie the muscles. 

 Schneider has divided the Nematoidea in accordance with 

 the arrangement of the muscular system thus: 1. Holo- 

 myaria (Gordius, Mermis). 2. Meromyaria (Trichina, &c.). 

 3. Polymyaria (Ascaris, Anguillula) . In the first division 

 there is a uniform, unbroken sheet of muscular tissue spread 

 beneath the dermis : in the second division the muscular 



layer is broken up into series of rhomboidal plates of mus- 

 cular tissue ; whilst in the third it is still more broken up, 

 and projects in masses into the cavity of the body. These 

 projections have been mistaken for glands by some observers. 

 A remarkable confluence of some of the muscular fibres along 

 the ventral line of the body, forming a sort of " raphe/^ 

 has been mistaken for the gangliated cord of a nervous 

 system. The nervous system is found in a ring surrounding 

 the trihedral pharynx, and presenting three ganglionic enlarge- 

 ments. Four trunks appear to proceed from this, but two 

 only can be traced, one along each water-vessel. The 

 pharynx is trihedral, and presents an enlargement, which 

 is worked by three powerful muscles, and serves as a pump. 

 In Trichina the gullet is extremely narrow, and obscured by 

 cellular growth; whilst in Mermis, the place of the alimen- 

 tary canal is completely taken up by a mass of cells, which 

 have received the name of corpus adiposum. The history of 

 the development and sexual conditions of the Nematoidea is 

 in many respects very interesting. 



Lecture IX. — Cucullanus elegans has two hosts, a fish and 

 a crustacean larva. Gordms and Mermis are parasitic when 

 asexual, but free when mature. Dracunculus, the guinea- 

 worm, presents a case in which there is a parasitic propaga- 

 tive state, but since no one has detected spermatozoa, the 

 idea is suggested that they reproduce by budding, as parasites, 

 but that, as Carter suggests, their sexual parents are free- 

 living Nematoids of the ponds and tanks. Sphoerularia is 

 another very strange case. In this there is no alimentary 



