SEA-FISHERIES LABORATORY. 253 



oblique muscles and the ventral body wall. In ripe 

 specimens there is often also a considerable mass of 

 genital products behind the third diaphragm, and pushing 

 it forwards into a pouch-like outgrowth (or two such out- 

 growths, one at each side of the alimentary canal). This 

 is due to the fact that while the perforations in the 

 diaphragm allow the passage forwards of the waves of 

 coelomic fluid (see p. 233), they do not permit the passage 

 of the ova, or spermatid masses, to any extent. These 

 are, therefore, as it were filtered out of the coelomic fluid, 

 and collect in a more or less compact mass behind the 

 ventral portion of the diaphragm. 



The genital products escape from the animal by 

 means of the last five pairs of nephridia, the terminal 

 vesicles of some of which are often found to bo distended 

 with ova or spermatozoa during the breeding season 

 (fig. 26). In a specimen 200 mm. long the vesicles of 

 some of the nephridia were 14 mm. long and 6 mm. in 

 width owing to distension by ova, while in another speci- 

 men the vesicles were filled with sperms, and were 5 mm. 

 in length and 4 mm. broad. The funnel of the nephri- 

 dium is usually widely open during the breeding season. 

 During the discharge of ova from the female the eggs are 

 caught in considerable numbers by the slimy mucus which 

 covers the body. Nothing further is known, however, 

 about the oviposition. Eipe females, with the coeloni 

 filled with ova, are found during the later portion of 

 February and during March, but by the end of the first 

 or second week in April the ova are usually all discharged. 



Nervous System. 

 The central nervous system is composed of the brain, 

 the oesophageal connectives, the stomato-gastric system 

 and the ventral nerve cord. 



