History of the Theory of Heredity. 45 



for the egg is, at no stage of its growth, unspecialized, 

 and it does not require the assimilation of " soul-stuff " 

 in order to develop into an organism. 



We must conclude, then, that however satisfactory 

 and accordant with observed fact the hypothesis of 

 epigenesis seems to be at first sight, more careful analy- 

 sis shows that it is in no sense a true explanation of the 

 phenomenon of development. ^ > 



The analogy between the evolution of the species from, 

 an unicellular ancestor, and the development of the indi- 

 vidual from an unicellular egg, is simply an analogy, for 

 the cause of the first phenomenon, the selection of con- 

 genital variations, is wanting in the second case, and 

 there is nothing to take its place if it is true that an egg 

 is really, like a rhizopod, an unspecialized cell. 



Haeckel's statement that heredity is memory, how- 

 ever true it may be, cannot be accepted as an explana- 

 tion, for we have no knowledge of the existence of mem- 

 ory apart from organization, and we cannot conceive 

 that an ovum can retain the memory of the past history 

 of its species, unless it possesses a corresponding organ- 

 ization. 



Jiiger's view that the embryonic ovum in unspocial- 

 ized, and that its specialization is gradually assimilated 

 during the development of the organism which contains 

 it, fails to account for the phenomena of reversion, and 

 to account for reversion he is compelled to assume that 

 the egg is organized from the time of its origin in the 

 developing egg of the preceding generation. 



In each case we are driven to the same conclusion, 

 that the epigenesis hypothesis is inadequate; and we are 

 forced to accept some form of the evolution hypothesis. 



This necessity has not escaped the notice of some of 

 our most acute thinkers. Huxley, for example, says 



