WEISMANN'S THEORY OF THE GERMPLASM 59 



7 8 9 10 

 15 16 17 18 19 20 21 22 



6 



11 12 13 14 



23 24 25 26 27 28 29 30 



In the three diagrams the nuclei with the same 

 numbers have the same rank in descent, and 

 therefore, according to the theory of Roux and 

 Weismann, have the same qualities, while the 

 nuclei with unlike numbers differ in qualities. 



Let us now notice how the nuclei in the three 

 processes of division, of which two are abnormal, 

 are placed in the mass of the egg. 



After the first division, the nuclei are alike in 

 all three cases ; after the second difference appears. 

 In Al and Bl nuclei 3 and 5 lie to the left ; 4 and 

 6 to the right of the second cleavage-plane, which, 

 according to Roux's hypothesis, corresponds to the 

 median-plane of the future embryo ; while in C 

 they are forced into two layers, one above the 

 other, nuclei 4 and 6 being dorsal, 3 and 5 ventral. 



In the third cycle of division there is no agree- 

 ment between the three cases. 



In the diagrams A2 and B2 the nuclei still lie 

 similarly to the right and left of the middle line ; 

 but in A2 they are arranged in two layers, in B3 

 in a single layer. The nuclei 8, 10, 12, and 14, 

 which compose the upper layer in A2, form the 

 middle of the disc in B2 ; and 7 and 9, 11 and 13, 

 the ventral nuclei of A2, occupy the ends of the 

 single-layered disc of B2, being closely pressed 

 against each other. 



