ii DEVELOPMENT OF MAN". 91 



study the human ovum in so early a develop- 

 mental stage as that of yelk division, but there 

 is every reason to conclude that the changes it 

 undergoes are identical with those exhibited by 

 the ova of other vertebrated animals; for the 

 formative materials of which the rudimentary hu- 

 man body is composed, in the earliest conditions 

 in which it has been observed, are the same as 

 those of other animals. Some of these earliest 

 stages are figured above and, as will be seen, they 

 are strictly comparable to the very early states of 

 the Dog; the marvellous correspondence between 

 the two which is kept up, even for some time, as 

 development advances, becoming apparent by the 

 simple comparison of the figures with those on 

 page 86. 



Indeed, it is very long before the body of the 

 young human being can be readily discriminated 

 from that of the young puppy; but, at a tolerably 

 early period, the two become distinguishable by 

 the different form of their adjuncts, the yelk-sac 

 and the allantois. The former, in the Dog, be- 

 comes long and spindle-shaped, while in Man it 

 remains spherical: the latter, in the Dog, attains 

 an extremely large size, and the vascular processes 

 which are developed from it and eventually give 

 rise to the formation of the placenta (taking root, 

 as it were, in the parental organism, so as to draw 

 nourishment therefrom, as the root of a tree ex- 

 tracts it from the soil) are arranged in an en- 



