54 N. ODHNER, NORTHERN AND ARCTIC INVBRTEBRATES. VI. PROSOBRANCHIA. 2 SEMIPROBOSCIDIFERA. 



The female orifice ( ? in the Fig.) leads into a vagina which hastlie wliole of its upper 

 side beset with a row of small vesicula? or spermatocysts {sp. c), some of tliem with 

 common ductuli. This fact is enough to place the genus in close relationshij) to the 

 Laniellaria group and to distingiiish it sharjily from Velutina and allied forms. The 

 liind part of the vagina is produced to a long coecal process, following the upper side 

 of the intestine towards the female part of the genital gland. Perhaps this process (o. d.) 

 is a survival of an ancient oviduct. 



A distinct bursa copulatrix {b. c. = Beiigh's »Schleim- und Eiweissdriise») emerges 

 from the front part of the vagina covering this on the outer and upper sides. Bergh 

 describes it in these words (P. 261): »es schienen zwei abgeplattete Höhlen vorzu- 

 kommen die vorne miteinander communicieren, eine obere kleinere und eine viel grössere 

 untere». The observation is correct, but the lower bladder is in communication also 

 with the vagina and may equally well be looked upon as an appendage of the latter. As 



?' 



fig. 1. Tlio Genital Apparatus of Marsenina glabra (Couthouy). 



this lower bladder (2>r.) in its histological structure is like the prostata gland of Velutina, 

 it must be considered as an homologon to that gland, and the upper bladder alone, lined 

 with a thick excretory epithelium consisting of denser cells, is the bursa copulatrix. In 

 Lamellaria and Chelynotus a vaginal diverticle is present with the same position as the 

 lower bladder and is perhaps its homologon in these forms. 



The male apparatus consists of a cylindric penis, combined with a vas deferens {v. d.) 

 running along the upper and outer side of the body-wall nuiscles to the right side of the 

 female orifice, where it opens into the vagina just above its orifice. The prostata gland, 

 mentioned (P. 261) and figured (Tab. U, Fig. 22) by Bergh, must be the true vagina 

 with its adhering spermatocysts. On Tab. U, Fig. 20, Bergh has indeed figured such 

 spermatocysts (their upper ends rise behind the »Eiweissdriise»). 



On the opposite (right) side of the vagina another du et opens, likewise close to the 

 female orifice; this is the hermaphrodite duct. It has the same appearance as in Velu- 

 tina, being in its lower part straight, becoming dichotomically branched backwards 

 into the hermaphrodite glandular tubes, and here containing the spermatozoids, while 

 the ova are formed in the peripheric ends of the glandidar tubes. 



