INITIATION OF DEVELOPMENT IN CELETOPTERUS. 33 



with i c.c. of 23/2 M KC1 + 99 c.c. of sea-water for 3-6 minutes, 

 whereas the best percentage of swimmers, 33 per cent., was 

 obtained with 5 c.c. oi 2 l /% M KC1 + 95 c.c. of sea-water for 3 

 hours. There is a decrease in maturation accompanied by an 

 increase in differentiation as length of exposure to KC1 increases. 

 Table VI. will serve to illustrate this point. It was found that in 

 general 3.5 per cent, of the 2 l / 2 M KC1 in sea-water acting for 

 45 minutes, was most satisfactory for inducing a high percentage 

 both of maturation and of swimmers. 



In normally fertilized eggs the requirements for both phe- 

 nomena, maturation and differentiation, are met at the same 

 time by the entrance of the sperm. Why, then, in the potassium 

 chloride eggs, should the two processes be, as it were, separated, 

 and the optimum conditions for one so far removed from the 

 optimum conditions for the other? It looks decidedly as if there 

 were a distinct set of reactions for the two processes, maturation 

 and differentiation. Whether potassium chloride shall arouse 

 only one, or both of these must be largely a matter of the condi- 

 tion of the individual egg, for in some eggs both processes go on 

 as a result of the potassium chloride treatment, while in the same 

 culture other eggs give only one of the two reactions, or give the 

 other very imperfectly. What those conditions in the egg are, 

 is entirely obscure. 



B. Details of Development Induced by Potassium Chloride. 

 F. R. Lillie has described the course of development of the 

 potassium chloride egg, in his papers of 1902 and 1906. In giving 

 the following account I shall be obliged to repeat many of his 

 observations in order to make the history as clear and complete 

 as possible, but I shall omit details largely. The eggs to be 

 described were from two sets of experiments, one using 7.5 parts 

 2^/2 M KC1 to 92.5 parts sea-water for one hour (designated set 

 A}, the other using 3.5 parts 2 1/2 M KCl to 96.5 parts sea-water 

 for 45 minutes (set B). The general behavior of the eggs in the 

 two series is very similar, and I shall describe now one, now the 

 other, without distinction. 



The Living Egg (Set B). The first polar body forms inside 

 15 minutes, the second, when formed at all, inside 30 minutes. 

 The eggs often form a polar lobe and appear to be attempting 



