418 SUMMARY OF CURRENT RESEARCHES RELATING TO 



and elseoblast; the ovarian cord, tlie male and female organs, and 

 the nerve-tube, the ganglion, the sensory organ, and the ciliated pit. 

 The endoblast of the embryo forms the endodermal tube of the stole 

 prolifer, and this the wall of the respiratory cavity, the ventral wall of 

 the gill-band, the digestive tract with the gland that surrounds it, 

 and the dorsal process. The pericardial cavity is at first a special 

 portion of the primary coelom, in which there are no isolated cells ; 

 one wall goes to form that of the heart, and the other that of the 

 pericardium ; it is stated that the finer histological characters of the 

 muscles appear to deserve further investigation. 



Individual Variations in the Structure of Simple Ascidians.* — 



Herdmann was the first to notice that the " vibratile organ " forming 

 the opening of the duct of the hypoganglionic gland in Ascidians varies 

 in form in different species. In general the aperture is single, but 

 in Phallusia mamillata and in Ascidia Marioni the duct of the gland 

 branches, and each branch opens into the branchial chamber by a 

 separate pore. M. L. Eoule now finds that a similar condition occa- 

 sionally occurs in Ascidia elongata Eoule, and Cynthia papillosa L. 



In the former species each of the eight branches of the duct opens 

 by a pore, and the eight pores are placed on a rounded prominence ; 

 but in C. papulosa the sixteen pores are each on a separate papilla ; 

 the group of papillae forming the "vibratile organ." The difference 

 between this organ in the first two species and in these latter forms, 

 is that, in A. Marionis and P. mamillata, the branches arise from the 

 main duct throughout its course ; whereas in the other two the 

 branches arise only from the peripheral part, near the apertures. 

 While this arrangement of the duct is a constant character in the first 

 two, it is only an occasional teratological phenomenon in the other two 

 forms. As to the cause of its presence in the latter case, the presence 

 of parasites or of debris, in the branchial cavity does not seem to 

 offer a sufficient explanation, for there is a remarkable regularity in the 

 arrangement of the pores. It is necessary to " look deeper into vital 

 manifestations, and to recognize that certain organs, although placed 

 in the interior and far removed from all direct external influence, can 

 vary in their structure to a considerable extent ; and this naturally, 

 without the embryo having experienced any artificial teratogenic 

 influences." 



The Phallusiadse of Provence.f — M. L. Eoule describes five genera 

 of the family Phallusiadse. The family is divided into the sub-family 

 Cionidse, in which the visceral mass is placed behind the branchial 

 sac ; and into the sub-family Phallusiadae, where the visceral mass 

 is at the side of the branchial sac. 



Of the Cionidge, two forms, Bhopalona neapolitana Philippi, and 

 Pleurociona Edwardsii n. sp., are described. B. neapolitana is piire 

 white near its free end, and has a very characteristic shape, being 

 divided into a branchial region and a visceral region, connected by a 

 narrow, elongated oesophageal region. The two siphons are near one 



* Oomptes Eendus, cii. (1886) pp. 831-3. 



t Eecueil Zool. Suisse, iii. (1886) pp. 209-58 (4 pis.). 



