TO THE EMBRYOLOGY OF AMPHIBIA. 87 



Postscript. 



While I was engaged in writing the present paper, an 

 interesting artiele by H. V. Wilson on the " Formation of the 

 Blastopore in the Frog Egg " appeared in Anat. Anzeiger Bd. 

 XVIII., No. 9-10, 1900, pp. 209-239. It appears that Wilson 

 and I have been studying independently the same subject at the 

 same time. Moreover the main results of his observations and 

 experiments by pricking the eggs, are largely in agreement with 

 mine, though there are some differences in details. 



The most striking points of agreement in our observations 

 are as follows : — 1. The blastopore is closed by the equal 

 overgrowth of the blastopore lip all around. 2. The first ap- 

 pearance and later growth of the archenteric cavity is brought 

 about, by the gradual accumulation of the intercellular spaces . 

 3. The vertical rotation of the Amphibian egg is caused by the 

 change in the specific gravity of the different parts of the egg 

 during the gastrulation. 4. The change in the specific gravity 

 of the différent parts is brought about by the enlargement of the 

 archenteric cavity, with the concomitant suppression of the seg- 

 mentation cavity, etc. 



The points of more or less difference between the results of 

 Wilsox and of myself are as follows : — 1. Wilson observes that 

 the " Ectoderm cells close to the dorsal lip, and close to the 

 ventral lip, gradually disappear round their respective lips. Such 

 cells, it would seem, must become a part of the archenteric 

 lining." This I can not corroborate from my materials. 2. 

 Wilson states that the ex-ovate produced by pricking the eggs 

 cannot be regarded as necessarily a fixed point, for the ex- ovate 



