IV. i INITIAL STRUCTURE OF THE GERM 



199 



TABLE XX 



Relation of dimensions of partial blastulae to their germinal value. 



Geniiinal values. 



Radii . 

 Surfaces 

 Volumes 



1 -j 



2 1-2 

 4 2-25 

 8 3-375 



8 



1 -75 



1 -5625 



1 4 



FIG. 110. Plutei of Echinus: a. ], b. I, c. J. The skeleton is 

 shown. (After Driesch, 1900.) 



From the proportionality of the number of cells to the germinal 

 value it follows that the cells of the whole and of the partial 

 blastulae are of the same size. 



If R, S, and Fare the radius, surface, and volume of the whole 



egg, and r n , s n , r n the corresponding magnitudes in a - larva, 



tt 



o r> J~ 



then s n . , whence r n = 7=. and therefore v n = . By 

 n Vn v n z 



this formula the germinal value of a larva of unknown origin 

 may be calculated. 



Finally, although segmentation takes place at the normal rate 



