WEISMANN'S THEORY OF THE GERMPLASM 65 



* 



The important point is that in both the experi- 

 ments, in the case of the frog and of the triton, the 

 cell-material, separated at the first cleavage, was 

 turned to a use quite different to its use in the 

 formation of a normal embryo. 



We may conclude with a very convincing proof. 

 In the above-mentioned abnormal development of 

 the frog's egg it happened that one edge of the 

 blastopore, on account of its weight, was very much 

 bent outwards. In consequence of this the cleft of 

 the blastopore lay between the normal blastopore- 

 lip and the everted border of the other lip. When 

 the notochord and the nerve-plate appeared, as a 

 result of this abnormal condition, they grew from a 

 cell-material that was quite different to that which 

 gives them origin in normal cases. 1 



In these cases Weismann cannot apply his 

 accessory conception, the existence of supple- 

 mentary idioplasm, only to the nuclei arising from 

 the first division ; he must extend it to the thou- 

 sands of embryonic cells that arise by division up to 

 the time for the appearance of the nerve-tube and 

 notochord. The behaviour of these cells under 

 fortuitously changed conditions shows them all to 

 be endowed with the capacity of development in 

 different directions. 



1 Further details concerning these experiments may be found in 

 HERTWIG, Ueber den Werth der ersten Furclmngszellen fur die 

 Organbildung des Embryo. Experimentelle Studien am Frosch- 

 und Tritonei. Archiv. fur Mikrosk, Anatomic, vol. xlii., 1893, 

 p. 710 ; Plate xli. ; Figs. 1, 2, 27. 



