54 



AUGUSTA ARNBAOK-CHRISTIE-LINDE, KORTHERN AND ARCTIO INVERTEBRATES. 



is quite separated from them. Seen from the left side of the zooid, the one bundle 

 of male glands is partly covered by the other, and the ovary has its position oppo- 

 site their middle line. If one imagines the gonads spread out, the ovary would thus 

 have its position between the two bundles of male glands. 



The oviduct extends from the above-described ovary between the two sperm- 

 ducts towards the brood-pouch, and opens into the distal part of the latter with a 

 very wide aperture (Pl. 3, fig. 53). The lumina of the brood-pouch and the oviduct 

 become thus distally confluent, and they communicate with the peribranchial cavity 

 by a short, narrow aperture which is well observable near the vas deferens (ef. text- 

 fig. 6). These facts are of a special interest; then, owing to the above-mentioned 

 arrangement, the passage of the egg is secured : the oviduct opening widely into the 

 brood-pouch, the egg, having left the oviduct, must be laid into the brood-pouch, 

 where it probably remains until it is fully developed. 



The oviduct is of considerable width, especially the distal part, which is rather 



Text-fig. 6. Kiikenthalia borealis Gottschaldt. Sections through 

 the genital pouch, ehowing the distal part of the oviduct and 



the rudimentary brood-pouch; cut obliquely. X50. 



bp. Brood-pouch. od. Oviduct. o. Opening into the peribranchial 



cavity. td. Vas deferens. 



sac-like, and the wall is deeply folded on one side. Fig. 55 represents a transverse 

 section of the genital pouch on a level with the bifurcation of the vas deferens. 

 The latter is on the point of forking, on account of which it appears somewhat 

 broad. The last-mentioned figure shows how the oviduct is somewhat compressed from 

 side to side; it is lined with a low epithelium. As appears from the same figure, 

 the ciliated epithelium of the vas deferens is well-developed. 



The brood-pouch has the form of a large double-walled sac with a constricted 

 neck. It generally contained one embryo. In some individuals it is of considerable 

 length and width, projecting beyond the genital pouch (text-fig. 5). Fig. 53 repre- 

 sents it at a stage somewhat less developed. 



In individuals containing no embryos a brood-pouch has also been observed, 

 though highly reduced with regard to form and size. Such an interesting stage is 

 shown by fig. 54, where the brood-pouch is represented by a short blind sac or an 

 appendix in connection with the oviduct; and in zooids with a rudimentary genital 

 pouch, as for instance in that represented by fig. 49, the presence of such a blind 

 sac can also be stated. Text-fig. 6 shows three transverse sections of the genital 

 pouch with the duets, which are cut obliquely. The brood-pouch is represented by 



