72 N. ODHNER, NORTHERN AND ARCTIC INVERTEBRATES. VI. PROSOBRANCHIA. 2 SEMIPEOBOSCIDIFERA. 



sequently ill Velutina velutina become an appendage to the male apparatus. Further, the 

 emerging point of the vas deferens in Marsenina being close to the female orifice, has 

 here moved backwards, and this also is the casewiththehermaphroditeduct. Thevagina 

 still belongs for most of its extent to the hermaphrodite portion, and the bursa copulatrix, 

 commnnicating as it does with the posterior part of the vagina, combines in itself both 

 a hermaphrodite and a true female natiire. 



Velu tin a pli c a ti 1 i s , Gullmarn (Text Fig. 3). The female orifice ( $ ) leads into a vaginal 

 säck of somewhat smaller dimensions than that in the preceding species. The bursa copu- 

 latrix emerges from its upper side, consisting of alargeuppersackandasmallerlowerone, 

 the former bladder-like, the latter (c*?/», c.) adheringon the outer side to the upper säck and 

 opening into it by a channel of communication from below. The epithelium lining these two 

 säcks consists of cylindric excretory cells. On the median side of the smaller säck, in front 



Fig. 2. The Genital Apparatus of 

 Velutina irelutina (Muller I. 



Fig. 3. The Genilal Apparatus of 

 Velutina plicatilis (Mijlleb) 



of the larger one, another small säck rises, lined at its apical end with a lower epithe- 

 lium; this saccule extends inferiorly and opens into the vagina. Just inside its junction 

 with the latter it forms, together with the vagina, a short diverticle receiving one lateral 

 and another more median duct close by each other. Tlie former or lateral duct appears 

 to be bipartite just near the starting-point; one of its partitions is directed backwards 

 to the prostata gland, which is of the same structure as in Marsenina and V. velutina, 

 though more simply lobated. The other partition runs forward on the upper side of the 

 muscle and is the vas deferens. 



The other of the two ducts debouching into the diverticle of the vagina, comes 

 from the hermaphrodite gland. This has the same composition as in the preceding spe- 

 cies and in Onchidiopsis, containing eggs in the peripherical folliculi and spermatozoids 

 in the inner or lower parts of the glandular branches. 



A comparison with V. velutina gives the following results: The vas deferens as 

 well as the hermaphrodite duct have moved far from the female orifice and have been 



wm 



