122 Artificial Parthenogenesis 



their permeability; the reverse would be much more 

 probable. 



Lillie's theory also fails to explain that mere treat- 

 ment of the eggs with a hypertonic solution can bring 

 about their development into larvae. This, however, 

 is intelligible on the assumption that the hypertonic 

 solution in this case has two different effects, first a 

 cytolysis of the cortical layer of the egg and second an 

 entirely different effect, possibly upon the interior of 

 the egg, which represents the second or corrective effect. 



McClendon 1 has shown that the electrical conduc- 

 tivity of the egg is increased after fertilization, and J. 

 Gray 2 has found that this increase in conductivity is 

 only transitory and disappears in fifteen minutes. 

 This might indicate that the egg becomes transitorily 

 more permeable for salts after the entrance of the 

 spermatozoon or after membrane formation; although 

 an increase in conductivity might be caused by other 

 changes than a mere increase in permeability of the 

 egg. The writer is of the opinion that it is necessary 

 to meet all these and other difficulties before we can 

 state that the alteration of the cortical layer, which is 

 the essential feature of development, acts chiefly or ex- 

 clusively by an increase in the permeability of the egg. 3 



x McClendon, J. P., Publications of the Carnegie Institution, No. 183, 

 '125; Am. Jour. PhysioL, 1910, xxvii., 240. 



2 Gray, J., Proc. Cambridge Philosophical Society, 1913, xvii., I. 



3 R. Lillie has recently shown that in a hypotonic solution water 

 diffuses more rapidly into a fertilized than into an unfertilized egg. 



