1 62 CARL RICHARD MOORE. 



usually produced a more or less typical membrane but later 

 cleavage was very abnormal. In many of the eggs there could 

 be seen more than one spermatozoon. 1 Following an exposure 

 to 39 C. and subsequent insemination, very few of the eggs 

 produced membranes, and cleavage if present at all, was very 

 irregular. After an exposure to 41 C.-42 C. and 45 C.-47 C. 

 no development was obtained by the addition of sperm. 



It is very evident that different eggs react to the heat stimulus 

 very differently. The eggs of Chcetoptems and starfish seem 

 to possess much less stability than do eggs of the sea uichin. 

 They are much more easily started out in their development. 

 Thus a slight rise in temperature is very effective in producing 

 cleavage in the two former but so far as the writer is aware al- 

 most entirely negative results have been obtained with the urchin 

 egg. In common with the more responsive egg however is the 

 fact that exposure to high temperatures causes a loss in the ca- 

 pacity for fertilization. It was in a study of the character of the 

 change effected in the egg that these few observations have been 

 made. The writer was not familiar with the experiments of the 

 Hertwigs with heat, at the time of his observations. The experi- 

 ments on the egg of Arbacia agree essentially with their earlier 

 observations in a study of the egg of Stronglyocentrotus lividus. 



The experiments were conducted by transferring washed Arba- 

 cia eggs into sea water, in a small beaker, the temperature of 

 which had previously been raised to that desired for the experi- 

 ment. The beaker was partially immersed in a water bath of 

 the correct temperature and a thermometer recorded the tempera- 

 ture of the two vessels. Eggs were removed from the beaker 

 of warm sea water at certain time intervals, transferred to finger- 

 bowls of normal sea water and inseminated with a fresh sperm 

 suspension. 



Many experiments were conducted using various temperatures 

 from 25 C. to 45 C. but only the results of a constant tempera- 

 ture will be reported at this time. 



Experiment.- Unfertilized eggs of Arbacia were exposed to 

 sea water of a temperature of 35 C., removed to normal sea 

 water and inseminated. The results are tabulated in Table II. 



1 Revealed by staining eggs whole. 



