80 OPISTHOBRANCHIATA OF BRAZIL 



of the gland is approximately marked by the dotted oval line. 

 It occupies the median posterior portion of the complex. The 

 distal end of the hermaphroditic ampulla, h. a., enters the con- 

 nective tissue stroma of the gland at its posterior end, giving off 

 the slender spermatic duct, sp. d., almost at right angles, and 

 then dilates into a broad cavity, 2.5 mm. in length and o.i mm. in 

 diameter. Its wall is practically identical in structure with that 

 of the hermaphroditic ampulla, and, like the latter organ, it is 

 packed full of spermatoza. It is probably to be regarded as a 

 fertilization chamber, since it is here that the ova first come in 

 contact with the spermatozoa from a different individual. Just 

 beyond the middle third of the gland complex this cavity bends 

 sharply at right angles, dilates somewhat, thence passes again in a 

 course parallel with the long axis of the gland, narrowing rapidly 

 to the exit of the uterine duct, u. d., from the anterior end. Just 

 as the above mentioned dilation begins to narrow, a more slender 

 duct, 0.24 mm. in diameter, is given off at an acute angle, running 

 sharply backward and ventrally, and opening into the cavity of 

 the albumen gland at its anterior end. This cavity is irregularly 

 pear-shaped in form, the broad end being turned forward and 

 outward, its tip extending nearly to the proximal end of the 

 gland complex. It is lined by a low cubical epithelium, with 

 large spherical nuclei. Into it open on all sides at intervals the 

 secretory alveoli of the albumen gland, which may be either 

 single, or, as is usually the case, branched into a small number 

 of divisions. The cells of the secretory alveoli are columnar, ca. 

 0.006 mm. in average height, with large conspicuous nuclei, but 

 their preservation did not permit making out any further details 

 of their structure. Dorsal to the entrance of the branch of the 

 hermaphroditic duct into the cavity of the albumen gland, a 

 somewhat broader duct passes forward into the cavity of the 

 nidamental gland proper. This large cavity occupies the ventral 

 portion of the nidamental gland throughout its whole extent, and 

 receives the short blind glandular diverticula which form the 

 mucous secretion. In general the cavity is undivided, save for 

 a few irregular ramifications along its posterior and outer border 

 into which secretory alveoli open. The lumen of the duct is lined 

 with small cubical cells with large nuclei ; in the posterior half of 

 the gland these cubical cells are replaced by tall slender columnar 



