NEMATODA I2 
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median dorsal one bearing two tactile papillae, and two lateral. 
The anus is a transverse opening close to the hinder end. The 
excretory opening is minute ; it is situated on the ventral surface, 
a little way behind the anterior end of the 
body. The female generative pore is also in 
the middle ventral line, about a third of the 
total length of the body from the head. The 
male generative organs open with the anus. 
The integument consists of a _ well- 
developed cuticle, which is turned in at the 
various openings. The hypodermis which 
lies under this cuticle is a granular layer of 
protoplasm, with scattered nuclei, Within 
this layer are the longitudinally-arranged 
muscle - fibres (Fig. 82). These are very 
peculiar cells, that part of them next the 
hypodermis is transversely striated, and con- 
tractile; the inner half, however, which is 
turned towards the coelom, is granular, and 
contains the nucleus of the cell. This mus- 
cular layer is broken up into quadrants by 
the presence of a dorsal, a ventral, and two 
lateral areas. The coelom, which is bounded 
by the granular portion of the muscle-cells, 
contains a fluid, but it is doubtful if this is 
corpusculated. There appears to be no 
splanchnic mesoderm surrounding the ali- 
mentary canal, and the coelom is probably 
not homologous with that of a Chaetopod, 
for instance. 
The alimentary canal runs straight from 
the mouth to the anus. The mouth leads 
Fic. 81.—A lateral into an oesophagus lined by an infolding of 
vee Siegen ee chitin, whose walls are very thick and 
yuris, to show 
the disposition of muscular, and its lumen is triradiate in 
the various organs. : ae 
Revor Caleb. transverse section. The oesophagus is 
1. Mouth. 2. Oesophagus. 3. Enlargement of the oesophagus armed with 
chitinous teeth. 4. Intestine. 5. Opening of the segmental tubes (placed by 
mistake on the dorsal instead of the ventral surface). 6. Testes. 7. Vas 
deferens. 8. Cloaca. 9. Papillae. 
