630 SUMMA.RY OF CURRENT RESEARCHES RELATING TO 



Genetic Cycle and Germination of Anchinia.* — Dr. J. Barrois re- 

 cognizes in the life-cycle of Anchinia one sexual and two sterile forms ; 

 in all these we may regard the bud as being primitively formed of an 

 ectoderm and eudoderm, the latter composed of cells of various kinds ; 

 there soon appears an endodermal nucleus, around which groups of 

 three different kinds of cells become arranged — these are nervous, 

 genital, and " disseminated." In the proliferous stolon this endoderm 

 forms a solid rod which is at first formed of cells of one kind only, 

 but which very soon becomes differentiated. The endodermic nucleus, 

 becoming constricted, forms on the ventral surface a pharyngo- 

 stomachal mass ; below is the nervous mass ; behind, the genital and 

 disseminated cells ; the first of all of these comes into relation with the 

 outer world by the buccal and anal orifices ; the pharyngeal mass 

 divides directly into pharyngeal sac and a pericardium, the endostyle 

 is not formed till later, when it arises as a small swelling of the 

 pharyngeal sac. In the sexual form the nervous mass is continuous 

 posteriorly with a large cord which passes between the cloaca and the 

 oesophagus, and terminates in a ganglion which is covered by the 

 genital mass. In one sterile form the coil is formed by the constric- 

 tion of a cylindrical nerve-tube, which extends along the whole 

 length of the embryo, whose anterior part corresponds exactly to the 

 entire nervous mass of the sexual form. It is very probable that 

 this cord corresponds to the large dorsal nerve which, in the Appen- 

 diculariae, connects the cephalic ganglion with the large swelling 

 which is formed at the base of the tube. The anterior swelling is 

 converted into a hypophysis, but it also gives rise to nervous parts of 

 great importance. 



The muscular layer divides into two bands, and then becomes 

 broken up into six semicircles in just the same way as in Doliolum. 

 The cloaca is the most important part which is formed by the ecto- 

 derm. The genital mass and the disseminated cells form for a long 

 time a mass which is placed posteriorly, and which in the sexual 

 forms gives rise to two genital glands, and in the sterile becomes 

 reduced to a few cells which are found in the neighbourhood of the 

 visceral ganglion. The disseminated cells unite into a ventral plate 

 which possibly represents the elseoblast. Especial attention is to be 

 directed to three points in which the history of their development 

 approximates Anchinia to the Append icularice : these are — 



1. The primitive constitution of the cloaca, the two short tubes 

 being comparable to the respiratory orifices of the Appendicular ioe. 



2. The presence of a nerve-tube along the whole length of the 

 body, and its termination by cephalic and visceral enlargements. 



3. The primitive presence of the anal orifice on the surface of 

 the skin. The formation of the cloaca at the expense of the ecto- 

 derm is a rare phenomenon. 



Anchinia may, in a sense, be regarded as representing a Doliolum 

 with six (instead of eight) bands ; the stolon is extremely like that 

 of Doliolum, but differs internally from that of any member of the 



* Journ. Aiiat. et Physiol. (Robin), xxi. (1885) pp. 193-267 (4 pis.). 



