BIOLOGICAL PHYSICS 



advantage of its services, so as to place in review, before 

 the " mind's eye," the manner and method of man's 

 growth, from the " monad " to the " cosmos " of organic 

 rank, by bringing forward, and naming in detail, a few of 

 the outstanding genetic features of his evolutionary pro- 

 duction, and mature being. 



To begin with the earliest stage of his developmental 

 evolution, we recognise in it the mutual amalgamation of 



FIG. 91. 



FIG. 90. HUMAN OVUM OF 12 TO 13 DAYS. (From Allen Thomson.) 



1. The ovum of the natural size with simply villous chorion. 



2. The same opened and magnified seven times. The large yolk-sac is seen with the 



embryo seen sidewise lying flat upon the yolk-sac. 



FIG. 91. HUMAN OVUM AND EMBRYO OF ABOUT 14 DAYS. 

 (From Allen Thomson.) 



A. The ovum opened, half the chorion laid to one side and the embryo and yolk-sac 



seen in the other ; natural size. 



B. The embryo and yolk-sac viewed from the dorsal aspect, magnified about ten 



times ; a, yolk-sac ; b, hind brain portion ; here for a space the medullary canal 

 is closed ; c, the mid-brain open superiorly ; d. hinder part of the medullary canal 

 also open ; e, portion of membrane, perhaps belonging to the torn amnion. 



two, Adamic, or parental, materio-dynamic entities (Fig. 

 88), the vital union of which founds the future organism, 

 and the survival of which, secures, and has secured, the 

 continuity of the human race, from " its cradle," to its 

 present generation and ensures its continuance into future 

 generations. In this earliest stage of development are 

 dimly visible, the working of the vital principles, which are 

 to govern the future progress of developmental change, as 

 well as, the method of unicellular life, which is continued 

 as such, under the advancing stages of developmental 

 progress, by cellular proliferation, and structural formation. 



