102 ARTIFICIAL PARTHENOGENESIS AND FERTILIZATION 



With this object in view, the following experiments were 

 performed. Membrane formation was produced by treating 

 eggs of S. purpuratus with butyric acid. The eggs were then 

 divided into two dishes containing the same hypertonic solution 

 (50 c.c. of sea-water +8 c.c. 2J m NaCl). One of these dishes 

 was maintained at a certain temperature, the other at a tem- 

 perature 10 higher. At different intervals, portions of the eggs 

 were replaced in normal sea-water of room temperature, and the 

 minimum exposure necessary to allow a certain percentage of the 

 eggs to develop was noted. The results for the eggs of five 

 different sea-urchins (S. purpuratus) are contained in Table 

 IX. One noteworthy result was that at temperatures above 

 20 C. the eggs were harmed by the hypertonic solution. Of 

 course, this does not hold for the eggs of all sea-urchins, as my 

 experiments at Woods Hole were usually performed at a tem- 

 perature of over 20 C. It is probably connected with the fact 

 that the temperature of the water at Pacific Grove never is as 

 high as that at Woods Hole in summer. 



TABLE IX 



temperature coefficient in settling this question. I myself applied this criterion to 

 the sphere of the physiology of development, and caused my pupils, C. D. Snyder 

 and S. S. Maxwell, to employ it in settling the question whether the heart beat 

 and the transmission of nervous impulses depend upon chemical or physical pro- 

 cesses. The temperature coefficient found in the heart beat was of the order of 

 magnitude for chemical processes. 



