THE PROBLEM OF ACTIVATION 247 



subject, for it is not complicated by the presence of 

 any unusual substance. % The action may be varied as to 

 both degree of temperature and period of action. A 

 third variable factor is the age of the eggs after placing 

 in sea-water; the only necessary statement in the last 

 connection is that the eggs of the starfish carry out 

 their entire maturation in sea-water, and that action 

 of increased temperature before the germinal vesicle 

 has broken down is not only ineffective but actually 

 detrimental to the subsequent viability of the eggs. 

 The condition of the eggs then gradually improves for 

 about an hour at the ordinary temperature of the sea- 

 water until the time of formation of the first polar 

 body, and from this optimum point the eggs deterio- 

 rate. The curve of condition for parthenogenesis coin- 

 cides with the curve for fertilization, as Delage (1901 a) 

 first showed. 



The method of experiment is to expose eggs in their 

 optimum condition to the temperature to be tested by 

 transferring to sea- water at the desired temperature, 

 and then to transfer samples back to sea-water at 

 normal temperature (i9-2i C.) at stated intervals. 

 The eggs undergo no visible changes in the heated 

 sea-water, but react when transferred to the normal 

 temperature. The following tables (p. 248) showing the 

 results at 31 C. and 32 C. will suffice for the discussion. 



The first table shows three separate experiments at 

 31 C. and two determinations for each experiment: 

 the percentage of eggs forming membranes and the 

 percentage developing to larvae; the second table shows 

 six experiments at 32 C. with only the latter determi- 

 nation. The folio wing points should be noted: (i) That 



