ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 43 



itleutical with that which bathes the suiTOimding cellular structures ; 

 Kowalewsky and Kupflfer had described the corresponding structure 

 in some other Ascidians as a solid gelatinous body. 



As observed by Hertwig, amoeboid cells migrate from the ectoderm 

 into the common mantle. A single Ascidiozooid was found to 

 consist of an internal endodermal sac and of a bilobate peritoneal sac 

 which communicates on one side with the endoderm by the branchial 

 openings and on the other with the exterior by the cloacal tube ; the 

 muscular fibres lie between the outer lamina of the peritoneum and 

 the ectoderm, as also do the heart and the reproductive glands ; the 

 products of the latter are transferred direct to the body-cavity. The 

 existence of a mesentery and the method of development of the buds 

 and of the embryo which results from the ovum, demonstrate con- 

 clusively that the Ascidians belong to the enterocelic type. The 

 glandular character of the endostyle is confirmed. The circulation of 

 the blood is wholly lacunar. Special attention is given to the repro- 

 ductive organs of the compound Ascidians ; in particular may be 

 noted the formation of a special oviduct in the Botryllidce, analogous 

 to that of the SalpcB, and the remarkable form assumed by the testis 

 in Ajplidium ; in the post-abdomen of the latter are found all the 

 elements of the primordial body-elements, viz. ectoderm, endoderm, 

 and peritoneal sacs. In a young Botryllid the nerve-ganglion was 

 observed to be in direct connection with a prolongation of the ciliated 

 fossa ; the muscular system in this form consists of smooth fibres, 

 placed between the ectoderm and the outer wall of the peritoneum. 

 The processes of rejuvenescence and of formation of new individuals 

 in compound Ascidians are described with great clearness. Metsch- 

 nikoff's discovery of the origin of the bud of Botrijllus from the 

 parietal layer on the right and left sides is confiirmed, and the foi*ma- 

 tion of the enterocele described. In the simple Ascidians, the 

 peritoneal sacs arise directly from the intestine and not from the 

 ectoderm, as maintained by Kowalewsky. 



New Division of Cheilostomatous Polyzoa.* — Dr. J. Jullien 

 considers that a character of capital importance has hitherto been 

 neglected by all authors, i. e. the ectocyst. The Membranipora lineata 

 of Linneeus is constructed on an absolutely diflerent type from that 

 of M. antiqua of Busk, but both are united in the same genus with 

 M. calpensis, which represents another type still, though derived from 

 the second. Turning to the characters of the ectocyst we find in 

 M. lineata a simple ectocyst that is not divided into two layers, and 

 true avicularia ; in M. antiqua there are two ectocysts, one external 

 and the other (cryptocyst) internal, having between them a solution of 

 continuity or hypostegia, no spinules but onychocellaria or false 

 avicularia. To this latter type belong a number of cretaceous and 

 some tertiary species which have hitherto been placed in numerous 

 genera, according to the form of the zoarium. For the opening of 

 the cryptocyst the author proposes the useful name " opesia," pointing 

 out that the term " apertui-e " has been used both for the oral aper- 



* Bull. Slc. Zool. Fraucc, vi. (1881) pp. 271-85 (5 figs.). 



