ARTIFICIAL PARTHENOGENESIS 643 
of sea-water upon development’ 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. I found that if we put 
unfertilized eggs into a mirture of 93 sea-water and 7 24n 
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 24n 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 larvee. 
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- 
1Journal of Morphology, Vol. VII (1892), p. 253. 
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