[108] Unless the egg is left so long in the pure NaCl solu­tion that its permeability is increased.

[109] Lillie, R. S., Jour. Morphol., 1911, xxii., 695; Am. Jour. Physiol., 1911, xxvii., 289.

[110] McClendon, J. F., Publica­tions of the Carnegie Institu­tion, No. 183, 125; Am. Jour. Physiol., 1910, xxvii., 240.

[111] Gray, J., Proc. Cambridge Philosophical Society, 1913, xvii., 1.

[112] R. Lillie has recently shown that in a hypotonic solu­tion water diffuses more rapidly into a fertilized than into an unfertilized egg. This is exactly what one should expect since the unfertilized egg is not only surrounded by the cortical layer but also by a thick layer of jelly both of which are lacking in the fertilized egg. It is difficult to understand how this observa­tion can throw any light on the mechanism of development, since water diffuses rapidly enough into the unfertilized egg.

[113] Delage, Y., Compt. rend. Acad. Sc., 1909, cxlviii., 453.

[114] Since this was written, two more of the partheno­genetic frogs over a year old died. Both were males.

[115] Loeb, J., Artificial Parthenogenesis and Fertiliza­tion, Chicago, 1913.

[116] Driesch, H., Science and Philosophy of the Organism. London, 1908 and 1909.

[117] Boveri, Th., Verhandl. d. physik.-med. Gesellsch., Würzburg, 1901, xxxiv., 145.