410 ANNUAL KEFORT SMITHSONIAN INSTITUTION, 1913. 



remained identical to the prirnitive reproducing cell, the successive 

 divisions of which have led to the formation of the being in ques- 

 tion. Here, again, the explanation of heredity is not difficult. The 

 new reproductive cell is identical to the primitive cell. It is ver}' 

 natural that its evolution should be identical to that of the last, on 

 one condition, however, that it finds, for its life and development, 

 conditions identical to those which the primitive cell found. Now, 

 these conditions exist for inferior beings; they live in the dense 

 ocean, which has a composition very nearly stable. If, however, the 

 conditions of development are artificially made to vary, either the 

 embryo dies, which is the most frequent contingency, or descend- 

 ants are obtained which differ from the parents b}^ their irregu- 

 larities, veritable stigmas of degeneracy (analogous to those of the 

 descendants of human beings, the physicochemical composition of 

 whose internal organs, of the blood, has been changed by sickness 

 or intoxication, as the children of diseased or alcoholic parents, for 

 example). 



Upon the whole, heredity is easily explained, as well as deviation 

 of heredity, as long as reproduction is a question of nonsexual beings, 

 which inherit their characters from a single parent, and not from two 

 at a time — the father and the mother. 



As to the sexual reproduction of beings, the embryologist also gives 

 us some very satisfactory explanations which accord very nearly with 

 those which observations give us as to the manner of heredity trans- 

 mission, and places in a vivid light in particular the facts observed 

 by Mendel and his successors. 



For sexually reproduced beings (we will speak, if you wish, only 

 of animals, but it is also the same with vegetable life) the egg — 

 that is, the primitive cell, the successive division of which will form 

 the new being — is constructed from the intimate fusion of two cells, 

 one of paternal, the other of maternal, origin, each one supplied from 

 a kernel. The particular point is the constitution of those sexual cells 

 from the kernel. Their ripening (that is, the moment from Avhich 

 they are susceptible of blending wnth the cell from the opposite sex 

 to form the egg by that fusion) is marked by a curious phenomenon. 

 One half of their kernel is expelled ; the kernel divides itself into two 

 with no special method ; one of the halves reaches the pole of the cell 

 and forms what is called the polar globule ; then it is expelled. Each 

 sexual element represents then a half cell, at least where the kernel 

 is concerned; but it is the seed which is important in hereditary trans- 

 mission. Here is proof of it : The sexual feminine cell is very large, 

 containing in certain cases a thousand times more protoplasms than 

 the masculine cell, which is very small and reduced almost to a seed, 

 or, rather, a half seed. However, paternal heredity is not less power- 



