TO THE LOWER ANIMALS 251 



Furthermore, there is a period in which the young of all 

 these animals resemble one another, not merely in out- 

 ward form, but in all essentials of structure, so closely, 

 that the differences between them are inconsiderable, 

 while, in their subsequent course, they diverge more and 

 more widely from one another. And it is a general law, 

 that, the more closely any animals resemble one another 

 in adult structure, the longer and the more intimately do 

 their embryos resemble one another : so that, for example, 

 the embryos of a Snake and of a Lizard remain like one 

 another longer than do those of a Snake and of a Bird ; 

 and the embryo of a Dog and of a Gat remain like one 

 another for a far longer period than do those of a Dog and 

 a Bird ; or of a Dog and an Opossum ; or even than those 

 of a Dog and a Monkey. 



Thus the study of development affords a clear test of 

 closeness of structural affinity, and one turns with im- 

 patience to inquire what results are yielded by the study 

 of the development of Man. Is he something apart ? 

 Does he originate in a totally different way from Dog, 

 Bird, Frog, and Fish, thus justifying those who assert 

 him to have no place in nature and no real affinity with 

 the lower world of animal life ? Or does he originate in a 

 similar germ, pass through the same slow and gradually 

 progressive modifications, depend on the same contriv- 

 ances for protection and nutrition, and finally enter the 

 world by the help of the same mechanism ? The reply is 

 not doubtful for a moment, and has not been doubtful any 

 time these thirty years. Without question, the mode of 

 origin and the early stages of the development of man are 

 identical with those of the animals immediately below him 

 in the scale : without a doubt, in these respects, he is far 

 nearer the Apes, than the Apes are to the Dog. 



The Human ovum is about ~ of an inch in diameter, 

 and might be described in the same terms as that of the 

 Dog, so that I need only refer to the figure illustrative 

 (14 A) of its structure. It leaves the organ in which it 

 is formed in a similar fashion and enters the organic 

 chamber prepared for its reception in the same way, the 

 conditions of its development being in all respects the 

 same. It has not yet been possible (and only by some 

 rare chance can it ever be possible) to study the human 

 ovum in so early a developmental stage as that of yelk 

 division, but there is every reason to conclude that the 



