564 H. P, KJERSCHOW AGERSBORG 



second type, sooner or later divides into a male and female 

 duct. These, however, do not open through distinct apertures, 

 but again unite to form a common atrium genitale or genital 

 cloaca.' 



The first type is also demonstrated by Bonnevie (1916) 

 for the pteropod Cuvierina columnella Eang, where 

 the hermaphrodite duct arises first as a groove (Kinne) and 

 later forms into a thin duct (Kohr) which makes its exit from 

 the left dorsal edge of the hermaphrodite gland. 



Type IV. — This is a new type. It is represented by the 

 reproductive system of Melibe leonina (Gould) and is 

 equivalent to types ii and iii plus a more complete duct system. 

 The organs of reproduction in this species (Pis. 28 and 37, figs. 9, 

 81) consist of a well-defined pair of gonads, each consisting of 

 many lobes or acini ; an oviduct, a ' prostate gland ' (con- 

 voluted portion of the female duct), a uterus (enlarged distal 

 portion of the oviduct), a spermatotheca, and a vagina ; a vas 

 deferens with its ampulla, a penis, and a mucous gland. The 

 male duct is further modified into vasa efferentia. Each of 

 these parts is peculiarly modified, and together furnish a 

 unique system of reproduction. The relative position of these 

 organs in the body-cavity is shown in PL 28, fig. 9. 



The male and female ducts in M. leonina do not unite 

 to form a common genital atrium as set forth by Lang for 

 'all Nudibranchia and a few Tectibranchia', but 

 open close together through separate apertures (PI. 37, fig. 77, 

 Mgjj) ; that is, the penis lies in front of the vagina (PI. 28, 

 fig. 9, P) ; in that way, it resembles the second type of Lang. 

 Both branch, i.e. a vas efferens and an oviduct pass to the 

 same acinus, which is to say : the hermaphrodite gland gives 

 rise to a double genital duct system which passes from the 

 respective male and female germ-cell area of the various 

 acini. In this respect the reproductive system of M. leonina 

 differs from all the three types of Lang, and for this reason I 

 have designated the genital duct system of this mollusc as 

 constituting a fourth type. However, since the oviduct 

 is still connected to the ampulla of the vas deferens by a duct, 



