ARTIFICIAL PARTHENOGENESIS 643 



of sea-water upon development 1 that so slight an increase in 

 the concentration of sea-water as is sufficient to induce par- 

 thenogenesis allowed the development of the eggs to go on 

 for at least twenty-four hours. / found that if we put 

 unfertilized eggs into a mixture of 93 sea-water and 7 2\n 

 NaCl solution, many eggs develop in the solution, and some 

 of them even reach the blastula stage and swim about. If 

 we use a mixture of 90 sea-water and 10 2^n NaCl solution, 

 the development stops earlier, for the simple reason that 

 such a solution is more injurious. Those facts show clearly 

 that the function of the artificial solution in the production 

 of parthenogenesis is that it has to deprive the egg of a 

 certain amount of water. In the majority of cases the 

 solutions that produce such an effect are at the same time 

 too injurious to allow the egg to develop or live long enough 

 to reach the blastula stage. This is the reason why we have 

 to take the eggs out of this solution and bring them back 

 into normal sea-water, if we wish them to develop into nor- 

 mal Iarva3. 



6. A consequence of the loss of water on the part of the 

 egg is an increase in its osmotic pressure. The osmotic 

 pressure inside the egg is furnished chiefly or almost ex- 

 clusively by electrolytes. It is thus not impossible that the 

 ions in the egg, if their concentration is raised, bring about 

 that change which causes the egg to develop. If we assume 

 that the spermatozoon starts the development of the egg in 

 the same way as in the case of artificial parthenogenesis it fol- 

 lows that the spermatozoon must possess more salts or a 

 higher osmotic pressure than the eggs. As I pointed out 

 in a former paper, this seems to be the case. But there is 

 no reason why the spermatozoon should not bring about the 

 same effects that we produce by reducing the amount of 

 water in the egg in some different way. At present, how- 



i Journal of Morphology, Vol. VII (1892), p. 253. 



