SOME POINTS IN EARLY DEVELOPMENT OF HEn's EGG. 167 



thin enough, and especially in osmic-acid preparations, nuclei 

 could be distinguished more or less throughout the whole 

 layer. In those cases where the peripheral thickenings of 

 this layer were well marked, these thickenings were seen to 

 possess numerous nuclei. The nuclei were never quite as 

 easily seen in the subgerminal layer as in the blastoderm 

 itself, as the former was more coarsely granulated. 



The nuclei were often arranged in clusters as if rapid 

 division were going on at this point, especially at the peri- 

 pheral thickenings. The irregularity of the segmentation of 

 these blastoderms precluded the possibility of determining 

 whether this subgerminal layer was in the first instance 

 deposited, as Bambeke and Klein believe is the case in 

 Teleostean Fishes, as peripheral thickenings which subse- 

 quently grew inwards and met beneath the blastoderm, or 

 whether this layer was a portion of the germ left behind 

 when the blastoderm was raised from the white yolk by the 

 appearance of the segmentation cavity. In the latter case 

 the subgerminal cavity would be more correctly described as 

 "intra-germinal." However, from the general appearance 

 the former view seems more probable. 



In some cases (as in fig. 6) the subgerminal layer seemed 

 absolutely continuous with a large mass forming part of the 

 blastoderm. This mass was nucleated almost throughout, 

 and its appearance was identical with that of the subger- 

 minal layer. In other cases smaller segments seemed as if 

 they were about to become separated from the subgerminal 

 layer, and in many cases it was absolutely impossible to 

 define the limits of germ and subgerminal layer, one passing 

 imperceptibly into the other. 



As we have remarked in the first part of this paper, in 

 some cases the vacuoles which appear so constantly in this 

 layer of which we are speaking were occupied by large 

 nucleated masses which seemed to lie free in the vacuole. 

 In other cases a vacuole might be seen to open on the floor of 

 the segmentation cavity, and a large cell-like mass was seen 

 lying half in the vacuole and half in the segmentation cavity. 

 The appearance of these blastoderms resembled very closely 

 those described and figured by Klein in the ova of Trout, so 

 much so that in many cases it would be impossible to distin- 

 guish them. 



It is clear that these observations resemble Goette's 

 to a certain extent; but we believe that there are some 

 very important differences between us. In the first place, 

 Goette regards the subgerminal layer as yolk. The fact 

 that the subgerminal layer gradually shades off into the 



