252 ON THE RELATIONS OF MAN 



changes it undergoes are identical with those exhibited 

 by the ova of other vertebrated animals ; for the formative 

 materials of which the rudimentary human body is com- 

 posed, in the earliest conditions in which it has been ob- 

 served, are the same as those of other animals. Some 

 of these earliest stages are figured below, 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 249. 



FIG. 14. A. Human ovum (after Kolliker). a. germinal vesicle. 



b. germinal spot. 



B. A very early condition of Man, with yelk-sac, allantois, 



and amnlon (original). 



C. A more advanced stage (after Kollikcr), compare fig. 13, C. 



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, becomes 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 

 form jt ion of the placenta (taking root, as it were, in the 

 parental organism, so as to draw nourishment therefrom, 

 as the root of a tree extracts it from the soil) are arranged 

 in an encircling zone, while in Man, the allantois remains 

 comparatively small, and its vascular rootlets are eventually 



