GENESIS OF MAN. 63 



theme gives rise, is the greater antecedent probability of like 

 organs, occurring in different animals, being homologous, than of 

 their being- analogous. The conditions in which life finds itself 

 placed are so infinitely variable, that the chances are almost infinity 

 to one against the development of the same organ independently 

 at two different times and places. Where the same organ is unex- 

 pectedly found in two animals which had not been supposed to be 

 at all related, it affords the strongest evidence that they are either 

 immediately connected by blood, or at least that they have both 

 descended from a common ancestor that possessed that organ. 

 Hence the irresistible force of the testimony afforded by the so- 

 called "rudimentary organs," which none but those who realize 

 this important law can properly appreciate. That analogues do 

 sometimes occur, in obedience to the law of adaptation, cannot, 

 however, be denied ; but they usually betray their origin by being 

 formed on an essentially different principle, though in such a man- 

 ner as to accomplish the same purpose. The wings of birds, bats, 

 and insects are such cases of analogy, in each of which the morpho- 

 logical differentiation is wholly different, while the physiological 

 function is the same. The beak of the Ornithorhynchus is perhaps 

 as near an approach as we have to a true morphological analogue, 

 the descent of that animal from the birds being overruled by a 

 preponderance of evidence against it. 



It is this principle, too, which conclusively negatives the pre- 

 sumption which some have advanced, that the aborigines of 

 America may have descended from the New World monkeys. 

 Catarrhine man could never have sprung from a Platyrrhine ape. 



It is, moreover, this same biological law which justifies Haeckel 

 in the assumption of so many hypothetical and long-extinct ances- 

 tral forms, although no warrant for them is afforded by paleonto- 

 logy. The Gastraea, the Chordonium, the Protamnion, the Pro- 

 mammalia, and the Pithecanthropus are all creatures, not of his 

 imagination, but of stern logic, based on a profound familiarity 

 with all the facts and principles that bear upon the problem. The 

 common origin and blood relationship of all creatures that possess 

 a spinal column, of all that are endowed with five-toed feet, of all 

 that develop an amnion, of all that have the double occipital con- 

 dyle, of all that suckle their young, of all having the fore and hind 

 feet differentiated into hands, of all that have the catarrhine nose 



