KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63- NtO 2. 55 



a short blind sac; like the oviduct, it is compressed from side to side. In text-fig. 

 6 a, the oviduct and the brood-pouch are still separated ; fig. b shows how the ovi- 

 duct opens into the brood-pouch, and in fig. c the opening into the peribranchial 

 cavity is visible. Whether this blind sac is to be regarded as a vestigial trace or 

 possibly as a rudiment of the brood-pouch, is a question which ought to be examined 

 in connection with that of the origin and formation of the whole complicated female 

 organ. As it is difficult to state anything for certain about the age of the indivi- 

 duals examined, we cannot draw any conclusions from the above-mentioned facts as 

 to the presence of a rudimentary brood-pouch, even before the first egg has been laid. 

 Another matter of interest is the question of the homology of the brood-pouch 

 in Kukenthalia. Before deciding it, it ought to be investigated whether the brood- 

 pouch of the species in question arises as a direct projection from the peribranchial 

 cavity, or whether it is possibly formed in connection with the oviduct with which 

 it, when fully formed, is so intimately connected. In other Ascidians in which a 

 brood-pouch develops to receive .the embryos, it is generally a diverticulum of the 

 peribranchial cavity. 



Test. 



Kukenthalia borealis forms colonies which are massive, usually rounded, and 

 not very large ; they are attached by a narrow base (Pl. 3, fig. 47). The zooids 

 are not arranged in systems, and the atrial as well as the branchial aperture of 

 each zooid opens independently on the surface. They form one layer and are placed 

 close to each other. The test of the colony is well-developed. Internally and at 

 the base it is soft and gelatinous, externally it is leathery. To that may be added 

 also that the capsules which surround the individuals are firm and tough. 



In my preliminary paper (1921) the occurrence of spicules in the test has been 

 mentioned. They seem to consist of calcareous matter. If put in some decalcifying 

 liquid — hydrochloric acid has been used — the crystals are dissolved. According 

 to the literature, spicules of various size and shape have been found in different 

 groups of Ascidians. However, the structures described under that name have not 

 been thoroughly investigated and their origin and chemical nature have not been 

 made out hitherto. According to Herdman they might be due to postmortem 

 changes, at least in certain cases (1882, p. 226). Modern men of science seem to 

 be of a contrary opinion. (Cf. Bronn's Kl. u. Ordn. d. Tierreichs pp. 230 — 234.) 

 Before further investigations of fresh material have been made, nothing can thus 

 be decided as to the importance of the spicules found in Kukenthalia borealis. 



The species in question was re-described by Hartmeyer (1903) under the new 

 generic name Kukenthalia. As the structure of the reproductive organs has been 

 made one of the chief characters in distinguishing the genera of the family Poly- 

 zoidae, the facts which have been ascertained by this investigation justify the for- 

 mation of a new genus. A comparative study shows that the above-mentioned organs 



