FERTILIZATION ON PARTHENOGENESIS. l6l 



urchin eggs to sea water, the temperature of which had been 

 raised to 35 C.-4O C. fertilization could be entirely prohibited 

 yet the eggs remained apparently normal and showed no signs of 

 cytolysis. 1 No attempt to restore the fertilizable capacity was 

 successful. 



Numerous instances are to be found in literature relative 

 to the powers of a rise in temperature to initiate development. 



Delage, 'oi, determined that starfish eggs developed partheno- 

 genetically if immersed in sea water of 30 .-35 C. at the 

 time of rupture of the germinal vesicle. 



R. S. Lillie ('15) found that exposing maturing starfish eggs 

 to a temperature of 29 .-36 C. for a short time produced no 

 visible changes in the egg; slightly longer exposures however led 

 to the production of typical membranes; but with scarcely no 

 further development the eggs break down before and after 

 cleavage. But an exposure three or four times as long as one 

 necessaiy to give rise to membranes, produces favorable develop- 

 ment and a large number of swimming larvae are obtained. 



Miss Allyn ('12) found a rise in temperature very effective in 

 producing cleavage and development in the egg of Chcetopterus. 

 Temperatures of 32.5 C. and 34.5 C. proved the more favorable 

 for cleavage and development of this egg: a small per cent, of 

 swimming forms were obtained. Temperatures of 35 C. and 

 above are less effective: no swimmers were obtained and cleavage 

 was very abnormal. 



The Hertwigs ('87) by subjecting the eggs of Stronglyocentrotus 

 lividus to abnormal temperatures determined that fertilization 

 after a certain length of exposure was prohibited. An exposure 

 of 5 minutes at 35 .-36 C. gave essentially the same results 

 as a ten-minute exposure to a temperature of 31 C. They 

 noted and emphasized the progressive effect of the higher ex- 

 posures, revealing again the quantitative aspect of whatever 

 changes are effected within the egg. In using a constant time- 

 five minutes the effect of a temperature of 31 C. was scarcely 

 noticeable, the process of fertilization was essentially normal: 

 at 35 C.-36 C. however changes were noticeable. The eggs 



1 Von Knaffi, '08, found that heating sea urchin eggs to 41 C. caused cytolysis 

 in a very short time. 



