526 DEVELOPMENT OF THE SIMPLE TISSUES, BY S. STEICKER. 



he considers to be not proven. The endoblast is perhaps developed 

 subsequently on the vitelline side. 



Waldeyer,* on the other hand, returned again to the view of Eemak, 

 that the mesoblast and the intestinal glandular layer proceed from 

 the originally inferior lamina. Waldeyer, however, independently of 

 Peremeschko, recognized that a great part of the cells subsequently 

 existing in the rudiment of the embryo wandered between the blasto- 

 dermic laminae. He was not, however, able to decide, so far at least 

 as regards the cells on the floor of the germ cavity, whether they are 

 descendants of the white yolk or are cleavage spheroids. 



That which His termed subgerminal processes he did not consider 

 to be a production of the epiblast, but as primary descendants of 

 the egg cells. 



I omit the statements of Peremeschkot and Oellacher,{ as 

 they constitute the basis of the account I here subjoin. 



A comparison of my account with the historical review 

 above given, shows that I, like Remak, consider the germ disk 

 of the fresh -laid egg to be composed of two laminae. I would 

 only add that the division into two is not always complete 

 throughout the whole extent, the laminae being sometimes still 

 intimately adherent, and the agency of the heat of incubation 

 is required to perfect their separation. 



The cells of the lower lamina change their form and arrange- 

 ment in the course of the first hours of incubation. They 

 become flattened; and appear fusiform on section (D, fig. 404). 

 After a few hours, thin sections of well-preserved specimens 

 show with perfect clearness, that two, and only two, layers are 

 present. The upper one is thicker and more compact, and is 

 often composed of two, three, or more tiers of cells; the lower 

 one consists of a number of flattened cells, appearing fusiform 

 on section. 



The inferior lamina was indeed, in the first instance, after it 

 had separated from the cloven germ, partially unicellular, 

 though in some parts projecting masses of cells were visible in 

 transverse section. I am unable to state what has in the mean- 

 while become of these cell masses. 



* Zeitschrift fur rationelle Medicin, 1869. 

 t Wiener Sitzungsberichte, 1868. 

 1 Loc. cit. 



