86 AKT. 3. S. TKEDA : CONTRIBUTIONS 



abnormal ways. That such are actually produced, as has been 

 brought out by the foregoing investigation, is solely due to the 

 isotropic nature of the Amphibian eggs so far as regards the 

 formation of the embryonic body. 



Consequently, I feel justfied in saying that the embryonic 

 body in Amphibia may be formed indifferently at any part of 

 the egg-surface according to the nature of the disturbing cir- 

 cumstances. 



It is needless for me to state that the isotropic nature of 

 Amphibian eggs has already been insisted on by many eminent 

 writers beginning with Pflüger, and including Born, O. Schulze, 

 etc. But it seems to me that most of these writers have been 

 inclined to place too much weight on the influence of gravity, and 

 have overlooked or underestimated a factor much more efficient 

 in the production of abnormalities, namely, the varying ratio in 

 which different parts of the blastoporic lip accomplish their task 

 in enclosing the yolk-mass — the ratio which determines, in re- 

 ality, the final closing point of the blastopore, and consequently 

 the position of the embryo. 



