IV. i INITIAL STRUCTURE OF THE GERM 



223 



areas. This continuity is soon lost and the egg becomes divided into 

 three regions, a clear layer spread over the animal hemisphere, 

 below this the yolk-mass with the fertilization spindle, and a large, 



FIG. 133. Dental-tutu. Normal cleavage. The red pigmented part is 

 represented by stippling. , Freshly laid egg, polar view ; b, the same 

 20 minutes later, after shedding the membrane ; c, the same from the 

 side ; d, one hour after fertilization, showing polar bodies ; e, first 

 division and protrusion of first polar lobe ; /, ' trefoil ' stage ; g, the 

 polar lobe has passed into CD; h, protrusion of second polar lobe (I '2) ; 

 i, second cleavage. (After Wilson.) 



nearly yolk-free area at the vegetative pole, which is now pro- 

 truded as the polar lobe. This becomes attached, as described 

 above for llyanassa, to the D blastomere. The first quartette of 



