INTERNAL ANAlOlVn'. 327 



Its extreme length, transverse to the longitudinal axis of the animal is 

 40.0 mm., its greatest antero-posterior width is 20.0 mm., while the thickness 

 of its bulkier portion on the left reaches 14.5 mm., thinning away toward the 

 right to some 7.0 nun. The dorsal surface is somewhat regularly convex, the 

 ventral one quite irregular, but in general concave, as are also the anterior and 

 posterior borders. The main bulk of this structure is made up of the nidamental 

 and albumen glands, the windings of which are closely interlocked in the one 

 common mass. An examination of Plate 5, fig. 4 will show its main relations. 

 The small hermaphroditic duct, sm. h. d, reaches the right posterior angle of 

 the adnexed genital mass, tapers rapidly to a third of its previous diameter, 

 and passes diagonally across the lower surface to its mid-anterior margin. Here 

 it curves around upon the dorsal face, forms there a broad loop and returns upon 

 the ventral surface, sm. h. d', to its posterior portion. Here the duct opens into 

 a small irregular cavity, the fertilization-chamber, /. c, lying deep between the 

 loops of the nidamental gland. 



Spermatocyst. — Into the same cavity opens the duct of Cuvier, d. C, or 

 duct of the spermatocyst. This organ, spc, Ues in close contact with the ante- 

 rior border of the anterior genital complex, to which it is bound by delicate 

 connective-tissue. It is of elongated cylindrical form with its blind end recurved 

 upon itself, and is shown in Plate 5, fig. 4 dissected free and raised slightly 

 from its close attachment. 



Immediately at the union of the duct of the spermatocyst with the fertiliza- 

 tion-chamber is found the opening of the copulatory duct, c. d. This duct is 

 continued to the right, uniting with the ovo-spermatic duct, ov. sp. d, to become 

 the left half of the large hermaphroditic duct, I. h. d. 



Albumen and nidamental glands. — Into the fertilization-chamber also 

 open the duct of the albumen gland, and the proximal continuation of the spiral 

 and convoluted portions of the ovo-spermatic duct, ov. sp. d. By a complicated 

 plication of the walls of this duct the massive nidamental gland is formed, 

 which makes up the bulk of the adnexed genital mass. 



Large hermaphroditic duct. — After the union of the copulatory and the 

 ovo-spermatic ducts they leave the right posterior border of the adnexed genital 

 complex and continue forward in a complicated series of loops as the large 

 hermaphroditic duct, I. h. d. A section across this structure shows that the 

 two ducts involved in it form simply the left and right halves respectively 

 of a single tube, separated from each other by thick folds from the dorsal and 

 ventral sides, which meet and interlock in the centre, thus dividing the lumen 

 into two nearly separate ducts. 



