38 THE CASE AGAINST EVOLUTION 



whereas members of the same species have very much in com- 

 mon, members of the same phylum have very little in common, 

 and members of different phyla show such structural disparity 

 that further correlation on the basis of similarities becomes 

 impossible (in the sense, at least, of a reliable and consistent 

 scheme of classification), all efforts to relate the primary 

 phyla to one another in a satisfactory manner having proved 

 abortive. 



Within the confines of each phylum, however, homology is 

 the basic principle of classification. But the scientist is not 

 content to note the bare fact of its existence. He seeks an ex- 

 planation, he wishes to know the raison d'etre of homology. 

 Innumerable threads of similarity run through the woof of 

 divergence, and the question arises: How can we account for 

 the coexistence of this woof of diversity with a warp of simi- 

 larity? Certainly, if called upon to explain the similarity ex- 

 istent between members of one and the same species, even the 

 man in the street would resort instinctively to the principle of 

 inheritance and the assumption of common ancestry, exclaim- 

 ing: "Like sire, like son!" It is a notorious fact that children 

 resemble their parents, and since members of the same species 

 are sexually compatible and perfectly interfertile, there is no 

 difficulty whatever in the way of accepting the presumption of 

 descent from common ancestral stock as a satisfactory solution 

 of the problem of specific resemblance. Now, it is precisely this 

 selfsame principle of heredity which the Transformist invokes 

 to account for generic, no less than for specific, similarity. In 

 fact, he presses it further still, and professes to see therein the 

 explanation of the resemblances observed between members of 

 the different families, orders, and classes, which systematists 

 group under a common phylum. This, of course, amounts to a 

 bold extension of the principle of inheritance far beyond the 

 barriers of interspecific sterility to remote applications that 

 exceed all possibility of experimental verification. Transform- 

 ists answer this difficulty, however, by contending that the 

 period, during which the human race has existed, has been, 



