HOLOBLASTIC AXD MEROBLASTIC SEGMENTATION. 



Ill 



the upper pole than the lower, and mirks the line of division 

 between the upper and smaller portion of the egg from the lower 



FIG. 104. Unequal segmentation of the Frog's tgg (after Eckeij in ten succe^ve stages. 



and larger portion, in which the segmentation proceeds much more 

 slowly than in the former. 



In partial segmentation we find a sharply marked contrast between 

 the formative and 

 nutritive parts of the 

 egg, inasmuch as the 

 latter does not seg- 

 ment. The terms 

 holoUastie and mz- 

 roblastiG therefore 

 have been applied to 

 total and partial seg- 

 mentation respec- 

 tively. 



Nevertheless, in 

 total segmentation 

 also, either groups of 

 segments of a definite 

 quality, or, at any 

 rate, a fluid yolk 



material may be Used FIG. 105. Segmentation of the germinal di&c of a Fc vd's egg, 

 for the nourishment ^face view (after Koaiker)'. ^germinal disc with the 



first vertical furrow ; B, the same with two vertical furrows 

 of the developing crossing one another at right angles ; C and L>, more ad- 



embryo. In fact, the vanced stagos with 8ma11 ceutral se s meuts - 

 contents of every egg consists of two parts (1) of a viscous albu- 

 minous protoplasm; and (2) of a fatty granular matter, the 

 deutoplasm, or food yolk. The first is derived from the protoplasm 



