76 



Geometrical relation of Nuclei 



I reproduce here figures from Sobotta, Samassa and Cerfontaine 

 which illustrate my point as well as possible (v. Fig. 36). 



In Samassa's figure A, for instance, the difference of the 

 position of the nuclei as regards its eccentricity is represented 

 by the figures 1 : 1-73 for the fourteen uppermost cells compared 

 with 1 : 2-40 for the twelve lower larger cells, the figure 1 repre- 

 senting the average distances of the centre of the nucleus from 

 the outer margin of the cell, the figures 1-73 and 2-40 the average 



Fig. 36. Drawings of sections of the gastrulating blast ula of Amphioxus, showing 

 how the nuclei of the cells occupy the position within their cells required by 

 the hypothesis explained in the text. A after Samassa, B after Sobotta, 

 C after Cerfontaine. 



distance of the centre of the nucleus from the inner margin of the 

 uppermost 14 and lowermost 12 respectively. 



It is a very remarkable fact that in all these figures the nuclei 

 of the invaginating cells occupy the position required by the hypo- 

 thesis. Moreover a similar state occurs in many other gastrulating 

 blastula, as, for instance, may be seen in the figures of Synapta by 

 Selenka, Balanoglossus by Bateson, etc. 



The condition that determines the position of the attraction 

 centre is probably the degree of concentration of the protoplasm. 



