18 NILS HJ. ODHNER 



parous gland (al.) debouches into the main duct. This is then 

 furnished with a sac-formed and thin-walled portion represen- 

 ting an undifferentiated receptaculum seminis or bursa copula- 

 trix; it was filled with spermatids. On its upper side, this sac 

 shows a tendency to a secondary dilatation (marked as cutaway 

 in the figure) half separated from the former by a fold which 

 protrudes from the bottom of the oviduct, and continues in the 

 distal narrow part of it dividing it longitudinally into two fur- 

 rows, the first step towards the development of a separate vagina. 

 Jn the male part of the genital apparatus only a simple 

 was deferens {v. d.) is present without accessory organs; it is 

 very short and penetrates into the penis which projects freely 

 from the body, like a curved unarmed papilla, its base being 

 surrounded by a circular preputial fold only. 



Affinities of Goniaeolis. 

 In the absence of all accessory organs such as prostata, 

 vesiculae séminales etc., the genital apparatus shows a very 

 simple organization; it is, in addition, concentrated to a relatively 

 small space and has rather short ducts. A rudiment of a 

 triaulic disposition is traceable in the bipartition of the distal 

 part of the oviduct, the one half of which represents a vagina with 

 a rudimentary bursa copulatrix, the other a distinct oviduct with 

 a spermatocyst. The very intimate connection of these portions 

 indicates a primitive condition, much more primitive than in 

 Äeolidia papulosa, where the separation of the ducts is per- 

 formed, or in Doridoeides, where also a separation of the 

 openings as in the Doridoidea, has taken place. Goniaeolis 

 approaches on account of the simplicity of its genital organs 

 the type of Pleur obranchus, but it lacks the prostata and the 

 well-differentiated vesicula seminalis. It might, however, best be 

 compared with Oscaniopsis, where, according to Vayssière (1901)'^ 



^ Monographie de la famille des Pleurobranchidés II. Am. Sei. Nat. Zool. 

 Vol. 12. Paris. 



