TETHYS DACTYLOMELA (RANG) 35 



ovoidal in shape, all its surface being convex, save the anterior 

 one, which is irregularly concave to correspond with the surface 

 of the posterior end of the liver and intestine, with which it is 

 in close contact. Its surface is finely lobulate, light brown in 

 color. From the antero-dorsal surface appears the light brown 

 small hermaphroditic duct, very strongly convoluted in its course, 

 0.20 mm. in average diameter, its length being approximately 

 45.0 mm., though this could be estimated only, as it was im- 

 possible to straighten out its windings. Its distal end passes 

 obliquely across the ventral side of the adnexed genital mass, 

 thence recurving dorsally to enter the latter. The "adnexed 

 genital mass" is a term applied by Robert ('89) to designate a 

 complex made up principally of the nidamental and albumen 

 glands and certain modifications of the genital duct. It is in 

 the form of a dorso-ventrally flattened cone, situated obliquely 

 to the longitudinal axis of the body. In the smaller specimens 

 it was nearly flat, in the largest one quite large and more pris- 

 matic in form, its ventro-anterior surface flattened, the dorso- 

 posterior one strongly arched. In length it varies from 2.0 mm. 

 to 13.0 mm., and in width from i.o mm. to 10.0 mm. The 

 texture of the largest one was very firm and somewhat brittle, 

 the great increase in size being due to the activity of the nida- 

 mental and albumen glands. The small hermaphroditic duct, 

 entering the anterior side of the basal portion of the mass, dilates 

 into an irregular cavity, the fertilization chamber, into which 

 open the duct of the albumen gland and the duct of Cuvier from 

 the spermatocyst. Beyond this fertilization chamber the genital 

 duct becomes very much convoluted for a short distance, passing 

 thence over into the spiral portion, which largely constitutes by 

 its windings the free portion of the mass, and incloses in its loops 

 the greater portion of the albumen gland. Throughout the turns 

 of this spiral one side of the duct is modified into the nidamental 

 gland by a series of complicated foldings, the lumina of which 

 communicate freely with the duct proper. Returning upon itself 

 from the apex of the mass, the spiral portion widens out into 

 the large hermaphroditic duct proper. By two longitudinal folds 

 from opposite sides of this large hermaphroditic duct it is in- 

 completely divided into two conduits. Owing to secondary twist- 

 ing the relation at first existing of a right and a left portion 



