no THE POPULAR SCIENCE MONTHLY. 



other. . . . That some such resemblance should, in fact, be found to 

 prevail is only what might naturally be expected, considering that each 

 full-grown individual is itself the result of a process of gradual devel- 

 opment from a sizeless and shapeless germ, in which development all 

 its organs equally participate," etc. Here, again, we encounter the 

 same argument from "necessity" that has just been considered ; and 

 here, again, it is no less preposterous than it was in its previous con- 

 nection. For to an embryologist nothing could appear more ridicu- 

 lous than the statement that " in such a case of gradual development 

 it follows, almost as a matter of course, that both the entire animal 

 and all its component members should, in their advance to maturity 

 from a mere pimctum saliens, exhibit some faint resemblance " to other 

 and allied animals. As a matter of fact, the resemblance is never 

 " faint " but profound, affecting all the structures which constitute 

 the essential framework of the organism. The kind of resemblance 

 on which the reviewer would appear inclined to place most reliance 

 would be a superficial resemblance of specific details. But although 

 even this is supplied by many facts — such as the hair on the unborn 

 child, clothing the body except on the palms of the hands and the 

 soles of the feet, which are also denuded in apes — it is not of so deep 

 a significance to a i^hilosophical mind as are the deeper resemblances of 

 anatomical structure. Hence, even if the unborn young of a higher 

 animal were, " at any stage of its development, identical with any of 

 the lower animals," the fact would not speak so strongly in favor of 

 its derivation from a lower form as does the fact of its passing through 

 a whole series of changes, each stage of which refers, in some point of 

 anatomical significance, to some stage in the existing grade of animal 

 organizations. Actual identity is not what the theory of descent with 

 modification would lead us to expect, seeing that, according to this 

 theory, the comparable features usually refer to features that are de- 

 rived from a common ancestor lower down in a branching stem of 

 descent. In a family tree we may expect the constituent members to 

 inherit in common some peculiarities possessed by their common an- 

 cestors, but we do not expect the personal appearance of all the indi- 

 viduals to be identical. Lastly, when we consider the enormous com- 

 plexity of organisms, the marvel is how the more complicated, in 

 attaining their higher complexity, mimic so closely the anatomical 

 structures of the organisms lower in the scale of complexity. Far 

 from its being " almost a matter of course," it is in the last degree 

 astounding that a vertebrated animal, for instance, should begin its 

 course of development by the same process of yolk-cleavage that oc- 

 curs in the rest of the animal kingdom, that its first differentiation of 

 body-layers should present the essential anatomical features of the 

 body-layers that characterize the jelly-fish, and so on. In short, when 

 any one at all acquainted with the facts of embryology regards them 

 e7i masse, the last of all notions to enter his mind will be that they 



