Early Development of Desmognathus Fiisca. 541 



this result, and there were indications that the eggs I studied gradu- 

 ally split off blastomeres at the animal pole and came to be roughly 

 of the sixteen-cell stage. 



Fig. 20 is a later stage where a number of the cells have divided 

 to form a rather coarse morula. In this and later stages there was no 

 evident indication of the location of the early segmentation planes. 

 Figs. 21, 22, and 23, show different views of the same egg in a later 

 coarse morula stage. Fig. 23, which is from below, shows relatively 

 few furrows at the vegetable pole. Sections of about this stage, 

 such as Fig. 51, show the complete division of the animal pole into 

 a number of well separated blastomeres with fine yolk granules, 

 forming a single layer of cells over a fair sized segmentation cavity, 

 while the vegetable pole is shown to be only partly divided into 

 blastomeres, that is even yet the large granuled yolk mass of the 

 vegetative pole is not completely separated into blastomeres. In this 

 and subsequent stages it will be noticed that the most complete and 

 most rapid division is in the region of the animal pole, where the 

 yolk granules are smaller, but division is by no means confined to it, 

 and the vegetative pole gradually becomes broken up into blastomeres. 

 As the rather irregular division proceeds, the smaller cells of the 

 animal pole become smaller and smaller, divisions of the vegetative 

 pole continue to be deeper and more numerous and the general appear- 

 ance of the egg on the surface is much like that of ordinary holo- 

 blastic eggs of frogs and salamanders; such as Figs. 21, 25, and 26. 

 Such stages seemed to be reached in about 24 to 27 hours after 

 laying, depending much up(5n conditions of temperature and moisture. 

 In a stage such as Fig. 25, the small cells of the animal pole are very 

 numerous, while those of the vegetative pole are quite numerous and 

 the cleavages deep, so all parts of the egg seem to be well divided into 

 cells. Sections of some of the less advanced fine morula stages, such 

 as Fig. 25, show the central part of the yolk mass to be almost undi- 

 vided, while at its periphery smaller cells may be seen which are 

 those seen in surface views. In such stages the region of separate 

 cells seems to begin at the animal pole and completely encircle a 

 central yolk mass, the few divisions on the lower pole have not yet 

 penetrated this central yolk. Fig. 53, of a section perpendicular 



