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THE AMERICAN NATURALIST [Vol. XLIX 



of hereditary separability whereby the body is a colony, 

 a mosaic of single individual and separable characters, 

 which is combined with a principle of hereditary correla- 

 tion whereby the body is a complex of minutely related 

 and interacting units so that functionally and structur- 

 ally many of these units are linked with others. Neither 

 principle is simple; on the contrary, both principles are 

 extraordinarily complex and go back to the very begin- 

 ning of things. Comparing more closely the observa- 

 tions on fossil vertebrates and invertebrates, we develop 

 laws of separability as well as laws of correlation, and 

 note that certain of these laws are far more clearly per- 

 ceived in some fields of observation than in others. 



The biologic value of the field to which our Paleonto- 

 logical Society is especially devoted lies in the revelation 

 of certain of these laws and causes of the separability of 

 characters which are not revealed at all to the zoologist 

 or to the experimentalist. The paleontologist is in a 

 position to understand ivhy certain characters fall apart 

 and become separable in cross breeding, the cause being 

 connected with their origin and antecedent history. 



Of far broader biologic significance is the fact that all 

 principles which may be discovered through paleontology 

 regarding the "origin of characters" in the hard parts, 

 go veri) alike characters of the soft parts as well as of 

 other structures and functions. For there can not be 

 one principle governing the "characters" of bones, an- 

 other those of the muscles, another those of nerves; one 

 principle for structures, another for functions. But 

 while these principles are unlimited, our comparisons 

 with zoology, for example, are limited to the origins of 

 characters which may be observed both in living and 

 fossil forms, namely, in the skeleton and in the teeth; 

 and at the outset a convenient and readily understood 

 distinction may be made between the origins of numerical 

 and of proportional characters, as follows: 



