642 SUMMARY OF CURRENT RESEARCHES RELATING TO 



to the generally received doctrine as to the provision of nature against 

 continuous interbreeding, he feels that, as yet, there is nothing to 

 show that self-fertilization cannot obtain in the case of the oyster. 



MoUuscoida. 



Development of Salpae and Pyrosomata.* — L. Joliet supports 

 the doctrines of Kowalevsky, as against the adverse views of Salensky, 

 Brooks, and Todaro. He finds that the gemmation of SalpcB is a true 

 gemmation, but one which is particularly complex from the fact that 

 " organs already differentiated take part in it, each on its own behalf." 

 To prevent ambiguity, the author proposes to define the stock organic 

 form as " that which, produced sexually and possessing sexual tissue, 

 either not yet differentiated, and simply in potentiality, or already 

 differentiated and recognizable, but being incapable of conducting 

 it to the term of its evolution, confides it for this purpose to one or 

 more successive forms, the last of which at least is sexual." 



The author thinks that a definition of this kind will be found to 

 apply to the Salpce, to the Pyrosomata (in which the third bud is alone 

 capable of reproduction), to the Doliola, to the compound Ascidia, and 

 several other animal forms. 



Structure of Anchinia.t — A. Kowalevsky and J. Barrois have made 

 Bome observations on this little-known Tunicate, a species of which, 

 A. rubra, is to be found at Villefranche, but it would seem to be rare. 

 Anchinia, like Pyrosoma and Doliolum, has the incurrent and excurrent 

 apertures directly opposite to each other, but it differs from the former 

 in having the lateral, and from the latter the median portions of the 

 cloaca rudimentary. 



On the whole Anchinia is the most complete transition form known 

 between the Salpce and the Ascidice. After a detailed account of the 

 general structure, the authors pass to the mode of gemmation ; in the 

 earliest observed stage the endostyle was found to be enormous, but 

 there was no cloaca, nor any means by which the bud could communi- 

 cate with the outer world. The bud, which is at first rounded, soon 

 becomes clavate, and there are indications of a division into body and 

 peduncle. The phai-yngeal and cloacal orifices become open to the 

 exterior, and the endostyle is proportionately smaller. After de- 

 scribing the succeeding stages, the authors deal with the question of 

 the affinities of this interesting form. 



The arrangement of the organs of the adult bears the closest 

 resemblance to what is found in Doliolum, and the resemblance of the 

 buds of the former is still more remarkable, and leads to the supposi- 

 tion that the AncMnice are Doliola which retain throughout life the 

 embryonic form of the buds of the latter ; there they separate from 

 the stolon, and becoming free, alter their organization so as to adapt 

 it to the fresh conditions of their existence. In Anchinia, on the 

 other hand, the buds remain fixed, and in that condition become 

 sexually mature. 



* Coniptes Rendu?, xcvi. (1883) pp. 1676-9. 



t Joiun. Auat. et Physiol., xix. (1883) pp. 1-23 (3 pis.). 



