ARTIFICIAL PRODUCTION OF NORMAL LARV.E 501 



III. IS IT POSSIBLE TO PRODUCE BLASTUL.E FROM UNFERTI- 

 LIZED EGGS WITHOUT RAISING THE CONCENTRATION OF 

 THE SEA-WATER? 



The early experiments with which I started had indicated 

 that an increase in the concentration of the sea-water caused the 

 segmentation of the nucleus in the fertilized egg. Morgan's 

 experiments had shown that the same influence may cause 

 the unfertilized egg to show a beginning of segmentation. 

 In Mead's experiments, however, there w T as practically no 

 increase yi the osmotic pressure of the sea-water, while the 

 nature of the ions seemed to determine the result. I wished 

 to find out whether a blastula could be secured from an 

 unfertilized egg without raising the concentration (the total 

 osmotic pressure) of the sea-water. All my experiment* 

 th us far have yielded the result that this is impossible, and 

 that by this method only a beginning of a segmentation can 

 be produced in an unfertilized egg. It goes without saying 

 that in these experiments bacteriological precautions are 

 necessary to guard against the possibility of the introduction 

 of spermatozoa by the instruments, or of their presence in 

 the sea-water. One has a pretty reliable criterion for the 

 entrance of a spermatozoon into the egg of Abacia in the 

 formation of the egg membrane. An unfertilized egg has 

 no distinct membrane, but immediately after the fertilization 

 a very distinct and rather thick membrane is formed. As 

 none of the eggs in the following experiment formed a mem- 

 brane or showed more than the beginning of a segmentation, 

 we may reserve the discussion of our methods of protection 

 against fertilization for the next section. Unfertilized eg^s 



C?c3 



of the same female were divided into three lots. One was 

 put into a solution of 90 c.c. -*u NaCl -f 2 c.c. | KOI + 

 2 c.c. y u CaCl 2 . After three and one-half hours a few of 

 the eggs showed a beginning of segmentation. After eight 

 hours a majority of the eggs had divided into from 2 to 4 



