LIFE HISTORY OF DESMOGNATHUS FUSCA. 



283 



to rupture easily. One must, however, remember the great 

 liability to imperfect preservation of the middle region of the 

 yolk, which might account for apparent imperfection of cell 

 walls. Although during the earlier part of development within 

 the egg, these yolk cells of the large type contain both large 

 and small yolk granules with, however, a preponderance of 

 the large ones, by the time the larva hatches practically all of 

 the smaller granules seem to have been consumed, and as a 

 result the large granules alone appear, and these not very closely 

 crowded together. It is from the cells of the smaller type, the 



vbv 



coe] 



sm 



FIG. ii. Detail of region indicated between the dotted lines in Fig. 10 (a). 

 Coel, coelomic cavity; sm, somatopleure; sp, splanchnopleure; vbv, vitelline blood 

 vessel; yl, yolk cells of the larger (nutritive) type; ys, yolk cells of the smaller type. 

 Abbe camera. X 273. 



peripheral ones, that the future epithelial lining of the intestine 

 will arise, while the large cells which form the bulk of the yolk 

 mass may be regarded as purely nutritive in function, since from 

 these apparently no tissue is derived. If this distinction goes 

 back, as seems probable, to the early differentiation of the cells 

 of the blastula into the peripheral ones containing small yolk 

 granules, and the central mass of cells containing large yolk 



