192 DR. A. ARNBAOK-CHRISTIE-LINDE ON THE 



generally bends somewhat to the side, extending along the inner 

 wall oi" the cavity. This arrangement was observed in all 

 specimens but one. In the latter, a rather large individual with 

 a strongly developed testis, the distal part of the vas deferens was 

 coiled up {cf. text-fig. 4 B), and its opening lies close to that of 

 the brood-pouch. 



As this arrangement has been found in a single individual only, 

 I do not venture to draw any conclusions fi-om it. The possibility 

 seems, however, not excluded that it might be of some impor- 

 tance for the fertilization, in this case probably the self-fertiliza- 

 tion of the individual. The fact that ova and spermatozoa are not 

 seldom found mature at the same time in the same individual 

 appears also to support the view that self-fertilization can take 

 place ; Avhether it is usual is another question. 



Though most Ascidians are hermaphrodite, it is, however, not 

 probable that self-fertilization generally takes place. On the 

 contrary, in many groups arrangements have been observed which 

 seem to prevent it. As an instance of such an arrangement, I 

 will mention that ova and spermatozoa are often produced at 

 difierent times, and are consequently not found mature together. 



From sections it appears that, in zooids belonging to colonies 

 caught in June, masses of spermatozoa fill up the sperm-ducts. 

 Other cells are macerated, but the spermatozoa are in good con- 

 dition — a fact which ought to be noticed, the material being 

 preserved in alcohol and dredged so many years ago. It confirms 

 the observation made many times before that the spermatozoa 

 are more resistant than other cells, and that they are highly 

 resistant, even to maceration. 



Female. — In zooids most advanced in development the female 

 organ consists of a small ovary with a wide oviduct and a very 

 large brood-pouch. 



As is shown by text-figure 5, a small rounded vesicle with a 

 wide duct is situated at the side of the male glands in the genital 

 pouch. Sections through it did not show much of its structure, 

 the tissues being rather macerated. The presence of eggs makes 

 it, however, evident that the vesicle is to be regarded as an ovary. 



In several individuals one very large egg, covered with follicular 

 -epithelium, was observed here, apparently ready to pass through 

 the oviduct (c/. text-fig. 7). 



As mentioned above, the ovary is placed at the side of the 

 male glands and 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 opposite 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 {cf. text-fig. 5). 

 The lumina of the brood -pouch and the oviduct become thus 



