STUDIES IN ARTIFICIAL PARTHENOGENESIS. 199 



soon as water enters or leaves the cell. It is probable therefore 

 that the effect is primary, and not the result of intermediate 

 changes. 



In normal fertilization, the sperm likewise produces coagula- 

 tive changes in the cytoplasm. Albrecht in 1898 showed that 

 there was an increase in viscosity after fertilization. He drew 

 his conclusions from observations on compressed eggs. I have 

 repeated Albrecht's observations a number of times. Much 

 more striking demonstration of gelatinization or coagulation 

 after fertilization is afforded by the centrifuge method. On 

 July 22, 1914, eggs from a single female were washed twice and 

 divided into two lots. At 10:00 P.M., half of the eggs were 

 fertilized. One tube of the centrifuge was then filled with fer- 

 tilized eggs, the other contained unfertilized eggs. At 10:10 

 P.M., the tubes were revolved for 18 seconds at an average 

 speed of 180.5 revolutions per second. The eggs were then 

 examined immediately. The unfertilized eggs were typically 

 stratified. On the other hand, the eggs which had been ferti- 

 lized were not at all stratified. Out of hundreds examined, 

 only one showed stratification and that was peculiar in lacking 

 an elevated membrane. Probably it had escaped fertilization. 

 The coagulative change begins to be apparent very soon after 

 fertilization. In one case the beginnings of the process could 

 be observed 2\ minutes after insemination. At 8:24 P.M. 

 (July 26) some eggs w r ere fertilized in a small volume of sea-water 

 and were shaken about to insure rapid sperm contact. At 

 8:26^ P.M., fertilized and unfertilized eggs were centrifuged 

 at the same time (in separate tubes). For 23 seconds an average 

 speed of 141 revolutions per second was maintained. Upon 

 examination the fertilized eggs showed some evidences of strati- 

 fication. The gray cap was becoming evident in some. But 

 most of the fertilized eggs showed little more than a tendency 

 for the pigment to mass at one pole. The unfertilized eggs were 

 clearly more stratified. They showed the gray cap plainly 

 in all cases, and a hyaline zone was also recognizable in them. 

 Thus only 2\ minutes after insemination, the sperm had already 

 begun to produce coagulative changes in the cytoplasm. 



From these experiments, I have been led to conclude that 



