PLATE G 



EXPLANATION OF FIGURES 



The early development of the blastodisc 



28 The animal pole of the 1.74 mm. oocyte shown in fig. 26. Zeiss apochromal 

 S.O mm. ocular 2. X 100. The finer reticulum about the germinal vesicle (g.v.) 

 is the first trace of the blastodisc which differentiates symmetrically about the 

 germinal vesicle (see fig. 8). 



29 An oblique section of the blastodisc of an oocyte of 5.47 mm. (see fig. 7. for 

 surface view). Leitz objective 2. X 55. Marginal (phi.) and central periblast 

 can be distinguished about the finely granular segmental disc. The more deeply 

 staining wedge granules (wdg.) have differentiated at the periphery of the disc. 

 The guide line g.v. runs to the group of chromosomes and nucleoli at the center of 

 the germinal vesicle. P.g., polar granules. A narrow break on the left sepa- 

 rates the wedge granules from the peripheral protoplasm. Final stage of period 

 of differentiation. 



30 The blastodisc of an oocyte 8 mm. long axis in life. Beginning of the final 

 growth period. Magnification as in fig. 29. The wedge (ivdg.) extends from the 

 periblast to the germinal vesicle and the group of polar granules at the edge of the 

 latter is well marked at p.g. Note the abrupt transition of the periblast into the 

 surrounding bed of white yolk; there is only a trace of a marginal periblast in this 

 egg. 



324 



