Mr. McCann’s predicament resembles that of the unlucky disputant, who having allowed a questionable major to pass unchallenged, strives to retrieve his mistake by picking flaws in a flawless minor. As Dwight has well said of the human body, “it differs in degree only from that of apes and monkeys,” and “if we compare the individual bones with those of apes we cannot fail to see the correspondence.” (“Thoughts of a Catholic Anatomist,” p. 149.) In short, there exists no valid anatomical consideration whatever to justify us in subtracting the human frame from the extension of the general conclusion deduced from homology. Whosoever, therefore, sees in the homology of organic forms conclusive evidence of descent from a common ancestor, cannot, without grave inconsistency, reject the doctrine of the bestial origin of man. He may still, it is true, exclude the human mind or soul from the evolutionary account of origins, but, if homology is, in any sense, a sound argument for common descent, the evolutionary origin of the human body is a foregone conclusion, and none of the anatomical “differences in degree” will avail to spare us the humiliation of sharing with the ape a common family-tree. It remains for us, then, to reëxamine the argument critically for the purpose of determining as precisely as possible its adequacy as a genuine demonstration. To begin with, it must be frankly acknowledged that here the theory of transformism is, to all appearances, upon very strong ground. Its first strategic advantage over the theory of immutability consists in the fact that, unlike the latter, its attitude towards the problem is positive and not negative. When challenged to explain the structural uniformities observed in organic Nature, the theory of immutability is mute, because it knows of no second causes or natural agencies adequate to account for the facts. It can only account for homology by ascribing the phenomenon exclusively to the unity of the First Cause, and, while this may, of course, be the true and sole explanation, to assume it is tantamount to removing the problem altogether from the province of natural science. Hence it is not to be wondered at that scientists prefer the theory of transformism, which by assigning intermediate causes between the First Cause and the ultimate effects, vindicates the problem of organic origins for natural science, in assuming the phenomena to be proximately explicable by means of natural agencies. Asked whether he believes that God created the now exclusively arboreal Sloth (_Bradypus_) in a tree, the most uncompromising defender of fixism will hesitate to reply in the affirmative. Yet, in this case, what is nowadays, at least, an inherited preadaptation, dedicates the animal irrevocably to tree-life, and makes its survival upon the ground impossible.