340 Comparative Anatomy — Its History, Aim, and Method 



important additions to it. As never before, it was realized that all living 

 things have much in common; that the same general plan of structure 

 may occur throughout some large group of plants or animals, merely so 

 modified in its details as to adapt members of the group to diverse en- 

 vironments and habits of living. The existence of what appeared to be 

 rudimentary, vestigial, and even useless parts was recognized. "Na- 

 ture" seemed to be a paradox of striking unity and endless diversity. 

 The more inquiring minds of the age found themselves confronted by 

 an insistent need for interpretation and causal explanation. To some of 

 these minds, the literal acceptance of the account of "Creation," as 

 offered by the dominant theology of the time, was unsatisfying. 



The period in question became highly controversial. It produced a 

 welter of ideas, often confusingly blended one with another. It is pos- 

 sible, however, to recognize three main centers around which the tides 

 of argumentation surged. One was the orthodox belief in "special crea- 

 tion" — that is, every existing type of organism originated by a "super- 

 natural" creative act, independent of preexisting types. A second 

 asserted that new types arise from preexisting types by a "natural*' 

 process — Evolution. Basic similarity between the new and the old is due 

 to inheritance; differences result from environmental or other agencies. 

 There is genetic continuity of all living things. A third view referred 

 "unity of plan" to a pure abstraction, an ideal or "archetype." For 

 the special-creationist, the archetype was a general plan upon which 

 the Creator molded various creatures, but modifying the details of the 

 plan to suit their diverse needs. Strangely, however, the idea of the 

 archetype was not restricted to special creation. In various more or less 

 vague ways, it became associated with the doctrine of evolution. This 

 anatomy of abstractions is now commonly called "transcendentalism." 



Linnaeus clung to "special creation," although in later life he ad- 

 mitted the possibility that a new species might arise in a hybrid be- 

 tween members of two specially created species. He was strongly 

 impressed, however, by the "unity of plan" observable in groups of 

 organisms, and saw in it the basis for a classification far more logical 

 and useful than any yet attempted. Early classifications defined a group 

 on the basis of one or few characteristics — and in many cases these were 

 superficial or irrelevant. Thus Aristotle separated animals into two 

 great divisions, those "with blood" and those "without blood." To him 

 all blood was red. John Ray (1628-1705) devised a far better classifica- 

 tion than any that preceded it but, even so, his two main divisions of 

 invertebrates were "Majora" and "Minora "--"larger" and "smaller" 

 invertebrates. Linnaeus, in his great work, the "Systema Naturae," 

 classified plants and animals, so far as his limited knowledge permitted, 

 on the basis of general structure. He elaborated the "binomial nomen- 



