TO THE EMBRYOLOGY OF AMPHIBIA. 6 



from the end of the blastula stage, spreading gradually upwards 

 and downwards, until finally it covers the entire surface of the 

 egg. And the fundamental parts of the embryonic body appear 

 certainly to be formed within this spreading zone. My desire to 

 subject these eggs to a thorough study by some new and suitable 

 method was realized in the spring of 1899 and of 1900 by using, 

 at the suggestion of Prof. K. Mitsukuri, the " Prismen-Rotator " 1} 

 of Zeiss, obtained by him and kindly placed at my disposal. 

 This instrument, as is probably well known, and as is fully 

 described in in the place cited, enables one to study the upper 

 and lower views of an egg as well as the lateral view of it from 

 any point in 300° of its circumference, without once touching 

 the egg and thus without the fear of calling forth abnormalities 

 by handling. The results of this study, together with some addi- 

 tional matter, are recorded in the following pages ; and although 

 I am not so sanouine as to think that I have found answers 

 to the questions propounded satisfactory to all, yet I hojoe that 

 the facts set forth will be received as some contributions toward 

 the final settlement of the problems. 



For the sake of convenience, I divide the present article 

 into four parts : — 



I. General Account of External Developmental Changes 

 in Ehacophorus Eggs. 



II. Observations upon Eggs of Rhacophrous, fiana, and 

 Bufo fixed on the Prismen Rotator of Zeiss. 



III. Exj^anation of the Facts observed in the Second 

 Part by Changes in the Interior of the Eggs brought out 

 in Sections. 



IV. Experiments by Puncture of Eggs. 



1) Zeit. f. wiss. Mikrosk. Bd. XIV. p. 304. 



