1896.] Embryology. 337 



The blastula obtained with the 5% solution the author attempts, with 

 some degree of plausibility, to make out to be of far reaching morpho- 

 logical importance. Whereas in all other cases development was either 

 more or less hindered or was abnormal, in this c;ise it was entirely sym- 

 metrical. The first indication of gastrulation appeared as a rim: sinking 

 about the equatorial plane and embracing the entire circumference. Sec- 

 tions showed a large mass of what the author calls passive yolk cells or 

 endoderm forming the lower half, while the upper half, composed of a 

 layer of ectoderm and one of active endoderm, forms a sort of cap 

 covering it. 



and, as the author points out, forms a gastrula that, if the passive yolk 

 be removed, very closely resembles tin tt*. From this 



it may seem more or less probable that ,r Lrastrnia 



may have been radially symmetrical, and that bilateral symmetry 

 appeared later. Further it appears that the upper or large invagina- 

 tion of the amphibian e-u is not the blastopore, but this is represented 

 by the entire circle including the yolk plug. 



It may be noted also, that if instead of supposing the passive ento- 

 derm to be removed, it be supposed to be greatly increased, one then 

 has a gastrula of the Btteroblastic type. 



Another point of interest is the manner in which the cells of the so- 

 called " active endoderm," or those bordering the equatorial ring, pro- 

 liferate. This proliferation according to the author has already begun 

 when the in -urfaee commences ; so tha: 



there being a pushing in of the outer surface, as the process is usually 

 described, there seems to be a pulling in. Whether this process is due 

 to the"cytotro])ism v described i.y Rouxfor the cellsof the dividing frog 

 egg, or to the taking up of the space occupied by the absorbed contents 

 of the blastula cavity, a- described by Hatschek tor Am/>hio.r)is, is not 



The embryos obtained differ from those obtained by O. Hertwig with 

 NaCl, in that the brain capsule does not close up and the dying away of 

 the brain matter does not take place, and again instead of the animal 

 cells breaking down as in NaCl, it is the yolk cells that crumble away. 



Finally one abnormal lithium chloride embryo has an adverse sig- 

 nificance for the concrescence theory. 



It is to be hoped that the author st a more ex- 



tensive paper, which shall he more fully illustrated.— F. C. K. 



