KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 63. NIO 9. 



15 



two epithelia coalesce at one point, viz. at the opening of the oviduct into the 

 peribranchial cavity. 



Della Valle (1. c.) investigated the reproductive organs of a Botryllid species 

 (probably Botryllus aurolineatus Giard). Though his description is incomplete and not 

 quite accurate, his statement about the presence of an oviduct is right. Whether the 

 structure so designated by him corresponds to what has been described under that 

 name in this note, is not, however, quite clear; jud- 

 ging from both the description and the figure given 

 b} 7 him, it does not seem probable that it is so (ef. 

 1. c. Pl. 6, fig. 48). Even if we suppose that the form 

 of the oviduct may vary relatively to different stages 

 of development that the organ in different individuals 

 has attained to, there are other differences still more 

 important, as clearly appears from a consideration of 

 what has been stated on the subject in the present note. 

 It may with good reason be questioned whether the 

 diverticula of the »cavitå del corpo o peritoneale» into 

 which, according to Della Valle's description, the Test . fig . 7 BotryUu* schiosieri Pallas. 

 oviduct opens, do not in all probabilitv represent the section through the femaie organs, xne. 



r A . c f- Cup-shapecl fold. ec. Ectoderm. em. 



true oviduets. Moreover, the structure described by Embryo. /. Outor foiiicie. o. Oyum. od. 



._ x , , , r , i c , • r Oviduct. p. Outer wall of tlie peribranchial 



Della Valle does not pertorm the tunction ot an cavity. t. Testis. 



oviduct, but rather that of a sort of sperm-duet: 



>Giunto 1'uovo a maturitå, questo cilindretto cellulare solido comincia a presentare nel 

 suo interno un canale, che estendendosi sempre pin, finisce per stabilire fra 1'uovo e 

 la cavita peritoneale una communicazione diretta, che deve servire al passagio de' 

 filamenti spermatici» (1. c. p. 465). 



Pizon too observed a duet »chez tous les Botryllidés», that was formed by the 

 outer follicle and opened into the peribranchial cavity. He agrees with Della 



Valle's view that it does not represent an oviduct but rather a spermduet: » 



— car jamais Tceuf ne franchit ce conduit: il sert uniquement a permettre aux 

 spermatozoides, qui errent dans la cavité péribranchiale, d'arriver jusqu'au contact 

 de 1'ceuf» (1. c. p. 290). Thus the true function and importance of the duet in 

 question was overlooked by Pizon. 



The figure illustrating the subject in question that is given by Seeliger in Bronn's 

 Tierreich, agrees in the main with Della Valle's and cannot be regarded as quite 

 accurate; the same may be said of the opening of the vas deferens shown in the same figure. 



Stage IV (Pl. 1 figs. 8—9. Text-fig. 7). When we compare with each other stages 

 II and IV, illustrated by figs. 7 & 9, the difference existing between the young and not 

 fully developed zooid, shown in the former figure, and the full-grown one, shown in 

 thelatter, is very striking. The full-grown zooid measures about 1.6 mm. in length. The 

 outline of the body is different owing to the changed condition of the reproductive 

 apparatus, which is externally manifested by the apparent disappearance of the large 

 ovaries that are visible on either side of the young zooid. The siphons are fully deve- 



