628 



In the normal egg after the first division similar protoplasmic 

 regions lie near to one another at the sides of the first cleavage plane. 

 Each such region will develop a part of corresponding organs. If 

 this juxtaposition be disturbed, as in Schultze's experiment and in the 

 experiment of rotating into a new position the uninjured blastomere, 

 then similar protoplasmic regions may be separated from one another 

 and such regions will tend to develop whole organs of half the 

 normal size. 



My own experiments have by no means been sufficient to work 

 out all of the details of this experiment. I have not been able to 

 obtain as much material as I had wished. Rather, however, than let 

 the results lie over for another year I have determined to publish 

 them because I believe they are sufficient to show that according to 

 the conditions of the experiment we may get half embryos or whole 

 embryos of half size from one of the first two blastomeres of the 

 frog's egg. 



Naples, April 11, 1895. 



Postscript. 



Since the preceding results were sent to press I have been 

 able to repeat twice the same experiments. Five half-embryos (Roux) 

 were obtained (from 92 eggs) when the black pole remained upwards 

 after the operation. 



When the white pole remained upwards after the operation the 

 results were not uniformly the same as those described in the pre- 

 ceding account. Seven whole-embryos of half size were obtained and in 

 addition three half-embryos (from 125 eggs). In one of these latter 

 the (half) medullary fold was for its whole length quite white in con- 

 trast to the dark ventral region. This shows that a rotation of the 

 protoplasm (beneath the egg-coat) must have taken place without 

 however producing a whole-embryo of half size. We must 

 therefore conclude that the rotation of the protoplasm is not the only 

 factor determining whether a half-embryo or a whole-embryo of half 

 size is produced. The results show nevertheless that after the rotation 

 a larger percentage of whole-embryos of half size are obtained than 

 of half-embryos. Further when the black pole remained upwards I 

 have in all cases only gotten half-embryos. 



Frommannsche Buchdrackerei (B ermann Fohle) in Jena. 



