ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 65 



caudal region of the ancestral digestive tube has undergone progressive 

 atrophy, and the vegetative functions have become more localized in the 

 anterior part of the trunk. This transformation of one part of the seg- 

 mented body of the vermiform ancesiors has affected all the trunk, except 

 the cephalic extremity and first segment of the body, in those forms whence 

 the Urochordata have arisen. (3) The af&uities between Uro- and Cephalo- 

 chordata are much closer than between either and the Vertebrata. This 

 graphic representation is suggested — 



Vertebrata Annulata 



Ceph alochor data 



Urochordata 



Protannulata, 



Anatomy of Amargecium torquatum.* — M. C. Maurice gives an 

 account of the heart, alimentary canal, and reproductive organs of the 

 compound Ascidian Amaraecium torquatum. A cross section through the 

 middle of the post-abdominal region reveals three cavities, of which the 

 median is shown to consist of an organ (epicardinm) depending from the 

 branchial cavity, v^hile the two others are prolongations of the pericardium. 

 The cardiac cavity is open, not only at both ends, but all along. The cleft 

 is situated on the convex face of the crescent formed by the heart, turned 

 from the epicardial sac, which cannot therefore close it. The cells of the 

 cardiac epithelium exhibit on the side of the heart-cavity a layer of muscle- 

 fibrils ; the nuclei on the other hand are situated towards the pericardial 

 cavity. Neither heart nor vessels exhibit endothelium. 



The tubular gland along the intestine is well marked. It consists of 

 many small tubes ending in culs-de-sac, and with a common canal conduct- 

 ing the secretion into the stomach. The anus has a large mouth and 

 several sphincter muscles. The cloacal cavity forms in the reproductive 

 period an incubatory chamber. In this the oviduct also shares. The cloacal 

 orifice bears a series of epithelial languettes. 



The reproductive organs are in the post-abdomen on the dorsal side. 

 The ovary is in front of the testis. The oviduct is well defined, attached 

 to the outer surface of the vas deferens. It is flattened, and lined by 

 non-ciliated epithelium, while the vas deferens is round and ciliated. The 

 ovarian cavity is continuous with the oviducal. The flat epithelium 

 becomes at certain points germinal, forming the follicles, from which the 

 mature ova drop off into the cavity. The ovary and testes are never func- 

 tional at the same time. 



Blastogenesis of Botrylloides rubrum.t — M. S. Jourdain dirputes the 

 accuracy of some of M. Giard's results with regard to the blastogenesis of 

 this Ascidian, and contends that blastogenesis, with the substitution of bud 

 for parent, is not confined to the postlarval life ; it is continiTOUs, that is to 

 say, it happens during the whole life of the stock, and is only accelerated 



* Comptes Eendus, ciii. (1886) pp. 504-6. See also this Joiu-nal, 1886, p. 955. 



t Comptes Rendus, ciii. (1886) pp. 1086-8. 



1887. F 



