NEMATODA 



125 



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 

 5— SJ^^H' 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 aU- 

 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 



P18. 81.— A lateral into an oesophagus hned by an infolding of 



—7 



view of a Nematode, chitin, whosc walls are very thick and 



Oxyuru, to show ' .... 



the disposition of muscular, and its lumen is tnradiate m 

 AftoGdeb.'"'^^'''" 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. 



