October 4, 1907] 



SCIENCE 



433 



that by treating the unfertilized eggs with 

 any acid, HCl, NHO3, oxalic, acetic acid, 

 CO2, he could cause the membrane forma- 

 tion, maturation, normal segmentation, and 

 the fonnation of normal larvae in a large 

 percentage of the eggs. In order to pro- 

 duce these results he put the eggs for about 

 five minutes into a mixture of 85 c.c. sea- 

 ■water plus 15 c.c. iV/10 acetic acid. 



These and similar facts may serve us as 

 a basis for the further analysis of the 

 nature of the process of fertilization. 



If we call forth the membrane formation 

 in the unfertilized egg of Strongylocen- 

 trotiis purpuratus, either by treating it 

 with benzol or with a fatty acid or with 

 alkali, the same processes take place at 

 first, as in the case of the entrance of a 

 spermatozoon; after some hours a normal 

 nuclear spindle is formed and the nucleus 

 divides regularly into two nuclei. This 

 shows that the synthesis of nuclein salts is 

 started by the membrane formation. If 

 the temperature is very low (from 2° to 5° 

 C.) the segmentation continues slowly but 

 regularly and a few normal blastulce may 

 be obtained. At a temperature of 15° or 

 more the development does not go beyond 

 the formation of the first nuclear spindle 

 or nuclear division ; soon after this the egg 

 begins to disintegrate in a characteristic 

 way. If, however, the egg is put after the 

 membrane formation for from 30 to 50 

 minutes (at 15° C.) into hypertonic sea- 

 water, all the eggs remain alive and de- 

 velop, provided the time of exposure is 

 chosen correctly ; and in a number of these 

 eggs segmentation and development occur 

 in a normal way. It is therefore obvious 

 that the calling forth of the membrane for- 

 mation in the egg starts the nuclein, synthe- 

 sis and the other processes of development, 

 but that the chemical processes do not 

 occur properly. Through the subsequent 



treatment of such eggs with hypertonic 

 sea-water these processes are carried back 

 into the proper channels. In some forms, 

 e. g., Thalassema and Asterina, the calling 

 forth of the process of membrane forma- 

 tion obviously suffices to start the chemical 

 processes in the egg in the right channels 

 and no after-treatment with hypertonic 

 sea-water is required. Our imderstanding 

 of the developmental effects of the sperma- 

 tozoon therefore depends upon the answer 

 to the three following questions: (1) AATiat 

 is the physico-chemical character of the 

 process of membrane formation whereby 

 this process is able to start the development 

 of the egg? (2) Why does it start this 

 development in some forms, e. g., Strongylo- 

 cenirotus piirpuratus, in the wrong chan- 

 nels? (3) In which way does the treat- 

 ment of such eggs with hypertonic solution 

 carry the development back into the proper 

 channels? We shall try to answer these 

 three questions in turn. 



As far as the physico-chemical character 

 of the process of membrane formation in 

 Strongylocentrot'us is concerned, we have 

 seen that it can be produced by very dif- 

 ferent means in the sea-urchin ; first, by fat 

 solvents, e. g., benzol, toluol, amylen, etc. 

 Since I had formerly expressed the sug- 

 gestion that the process of membrane 

 formation might be due to a coagulation 

 and since it might be argued that the above- 

 mentioned agencies might also have a slight 

 coagulating effect, it was of importance to 

 make certain Avhether they really act only 

 through their fat-dissolving power. Ben- 

 zol has a high fat-dissolving power and 

 an extremely slight coagulating effect on 

 proteins. Phenol, on the contrary, has a 

 much smaller fat-dissolving power but a 

 very great coagulating effect. If the 

 process of membrane formation were due 

 to a coagulating effect of these agencies, 

 phenol should act much more powerfully 

 in the membrane production than benzol; 



