88 



Geometrical relation of Nuclei 



speak of deuterogenesis being the direct and inevitable consequence 

 of the general structure of the unsegmented egg. It depends upon 

 the doubling of the expanding area upon itself. 



This may be recognised more clearly by a glance at the diagram, 

 Fig. 40. 



Let A represent a section of a sphere composed of living cells, 



Fig. 40. A, a diagram representing the blastula stage. B, the gastrula. (7, an 

 embryo after growth in length has begun, the effect of which is indicated by 

 the dotted lines. Theoretically closure of the blastopores should precede 

 accumulation. Actually the two processes go on together as in the diagram. 



which are actively dividing. The divisions occur only, or at any 

 rate chiefly, in the radial plane and, we will imagine, with equal 

 rapidity at all points. If this occurs in conjunction with the 

 growth of the divided cells to their "normal" size, the result 

 must be general increase in the size of the ring, or sphere, of which 

 the ring is supposed to be a section. The radial symmetry is in 

 no wise necessarily disturbed. For, given any point therein, the 



