APLYSTA. 243 



whiteness of the mucous gland. Like the latter it shows 

 transverse stripings due to internal septa, but these are less 

 regular than those of the mucous gland. 



The large hermaphrodite duct (la* herm. d.) arises from 

 the right anterior portion of the genital mass, close to the 

 point of entrance of the little hermaphrodite duct. It connects 

 the accessory genital mass with the common genital aperture, 

 conveys the egg ribbon and the sperms to the exterior, and 

 receives the foreign sperm. All three products pass through 

 the same aperture, which is undivided and is therefore described 

 as monaulic, in contrast to the diaulic condition in Tritonia, 

 where male and female ducts separate, and to the triaulic 

 condition in Doris, where the male, female, and copulatory 

 portions of the duct are distinct. The large hermaphrodite 

 duct is divided into a posterior and anterior portion, the two 

 being abruptly marked off both internally and externally. 

 The posterior part lies between the accessory genital mass 

 and the swelling called the bursa seminalis (b. sem.), the 

 anterior part between the bursa and the external aperture. 

 The former portion lies in the connective tissue beneath the 

 sub-pallium, the latter is embedded in the muscles of the 

 sub-pallium. 



The posterior portion of the large hermaphrodite duct is 

 divided longitudinally into two parallel divisions separated 

 internally by folds, but readily discernible externally owing to 

 a difference in appearance. The portion on the left, which is 

 the vaginal portion of the duct (vag.), into which the penis is 

 thrust during copulation, is straight, that on the right is thicker 

 walled and sacculated (od.), and conveys the egg cordon to the 

 exterior. The part along which the sperms pass on their way 

 outwards is not visible externally. 



At the anterior end of this portion of the duct a slight 

 constriction occurs. On the left or vaginal side a glandular 

 pouch, the bursa seminalis (b. sem.), is present ; on the right side 



