796 SUMMARY OF CURRENT RESEARCHES RELATING TO 



longitudinal sides of the branchial sac are formed by projections into 

 the branchial cavity, which develope into elongated papillae, then 

 meet and fuse by their ends. The cloacal orifice has a bilateral 

 symmetry. 



The authors regard as renal vesicles small closed cavities of vary- 

 ing form which project from the digestive tract ; a few connective- 

 tissue cells grouped into an irregular mass bound a quite small cavity 

 which appears in the form of a vacuole. The contents of the vesicles 

 in young individuals are always clear and hyaline, but it cannot be 

 doubted that their future function is renal ; they are developed from 

 mesenchymatous cells united into a small aggregation ; and we have 

 here a remarkable example of the formation of a secretory epithelium 

 from connective-tissue cells. 



The sexual organ may be distinguished in comparatively early 

 larvffi, where it is formed of a mass full of connective cells and of a 

 cellular cord arising from this mass; the former has indefinite 

 boundaries, owing to the peripheral cells having fine anastomosing 

 prolongations. The cord is early formed of a single row of fusiform 

 cells placed end to end. The whole mode of their further develop- 

 ment is at first sight very different from that of the same organ in the 

 Vertebrata ; but it is more superficial than real, as the authors hope 

 to show in another essay. 



The visceral ganglionic cord is to be seen in all stages of the 

 development of the embryo, and it presents a striking resemblance to 

 that of a young Appendicularia, as described and illustrated by Fol. 

 The hypophysial organ always appears as a tube ending in a cul-de- 

 sac ; in it we may distinguish a funnel-shaped opening into the 

 branchial cavity, a canal lying beneath the brain, and a terminal 

 swelling. 



The coronal circlet is at first a quadrilateral organ elongated 

 transversely, and distinctly bilateral ; there is at first a tentacle at 

 each right and left angle ; later on tentacles appear at the anterior 

 and posterior angles ; then there appear four new tubercles ; notwith- 

 standing the apparent radial symmetry of the adult the circlet and 

 the mouth are distinctly bilateral. 



The Synascidian Diplosomidse.* — M. S. Jourdain finds that the 

 bud which will give rise to a new Ascidian does not, as has been 

 supposed, arise from the pyloric but from the oesophageal region of the 

 parent. It appears as a projection, in the form of the finger of a glove, 

 not only from the mantle, but also from the digestive tube ; the bud 

 rapidly divides into two parts, one of which forms the thorax, the 

 oesophagus, and the rectum, and becomes very distinct from the other ; 

 it soon gives rise to a branchial chamber, and takes on a Y shape. 

 The second part becomes hollowed out into a tubular U-shaped cavity, 

 and forms the median part of the digestive tube, and, perhaps also, the 

 genital gland. There are not, therefore, two distinct buds but two 

 parts of one which was primitively single. The division of the 

 Diplosomidse cannot be retained. The author discusses the spur-like 



* Comptes Pendus, c. (1885) pp. 1512-4. 



