58 COSMIC PHILOSOPHY, [pt. u, 



natural selection of such variations might well be pronounced 

 incapable — save in very rare instances — of working entirely 

 analogous results in organisms so genetically distinct as 

 monodelphians and didelpbians, or as vertebrates and mol- 

 lusks. In other words, natural selection, acting upon such 

 fortuitous individual variations, would tend to produce in- 

 definitely increasing differentiations in many directions. 

 Such differentiations are to be seen in the amazingly elabo- 

 rate contrivances for the fertilization of orchids, the expla- 

 nation of which is one of Mr. Darwin's most brilliant 

 achievements. But when it is admitted that a great num- 

 ber of similar adaptive variations must be simultaneously 

 occurring in the same direction, then it is obvious that the 

 natural selection of such variations may often produce ana- 

 logous results in different genera and families, or even in 

 different orders, classes, or sub-kingdoms. Mr. Mivart 

 alleges the many resemblances between whales and the 

 ancient ichthyosaurians, as hardly explicable on the theory 

 of the selection of fortuitous variations. But when we recol- 

 lect that the vertebrate structure of mammals is at the out- 

 set homologous with that of reptiles, and that direct adaptation 

 must of itself tend to produce similar variations alike in 

 mammals and in reptiles which pass from a terrestrial into an 

 aquatic environment, the resemblance between a whale and 

 an ichthyosaurus ceases to be an enigma. The superficial 

 resemblance of a whale to a fish is a fact of like nature. 

 And in the case of amphibious carnivora, like the seal, direct 

 adaptation to a partially marine environment has aided in 

 producing fish-like limbs, while it has not interfered with 

 the general likeness of the animal to certain families of land 

 carnivora. So in the case of the pterodactyl as compared 

 with carinate birds, we begin with skeletons constructed on 

 the same plan, and we may expect to find that direct adapta* 

 tion to the necessities of flight will tend to produce similai 

 modifications of the shoulder-structure. But since, befora 



