164 Introduct{o7i to Aiiimal Morphology. 



acicular papillae ; no head fissures. The larvae are provided 

 with eyes, which are usually absent in the adults. 



2. Enopla — nerve ganglia nearly double; globular, lateral 

 nerve trunks within proper muscular walls ; mouth in front of 

 the nerve commisures, ventral ; no metamorphoses. This in- 

 cludes one family, Amphiporidae, with two muscular coats 

 only, an outer circular and an inner longitudinal, a proboscis 

 of three parts, anterior or basal, with seven coats, middle 

 armed with the stylets, and posterior saccular, with two mus- 

 cular coats. The bodies are generally short, with a long pro- 

 boscis, except in Nemertes. There are three blood-vessels 

 and two cephalic arches. 



Rhamphogordius {Raihke) — a thread-like, dioecious or 

 monoecious, jointed worm, with only longitudinal fibres and 

 two terminal, proboscis-like lobes, is placed by some among 

 the Enopla, but by Schneider is regarded as forming a sub- 

 division of Nematodes under the name Gymnotoma. 



CHAPTER XXIV. 



CLASS 2. — COTYLIDEA [Va?i Bciieden). 



Endo- or ecto-parasites (sometimes only temporarily 

 so), with cup-like or irregular suckers formed of pro- 

 cesses of the muscular lamina of the body wall, covered 

 with skin. They have no body cavity, sometimes no 

 intestine, never an anus, and are ciliated in early life, 

 but shed their outer layer. To this variable group 

 belong two orders : — 



I. Cestodea [Rtidolpln], tape-worms — hermaphro- 

 dite, segmented, endo-parasitic, band-like persona?, 

 with no digestive nor vascular system ; nourished by 

 osmose. The first segment (Head, Nurse, Scolex) is 



