248 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



established entelechy as the ultimate basis of individual 

 organisation, we shall be able to gain more satisfactory 

 ideas with respect to the meaning of the non-causal but 

 necessary connection, embraced in the concepts of type and 

 of correlation of parts. 



The type is a sort of irreducible arrangement of 

 different parts : the correlation deals with the degree and 

 the quality of what may be called the actual make of the 

 parts, in relation to one another : all ruminants, for 

 instance, are cloven - footed, the so-called dental formulae 

 are characteristic of whole groups of mammals. Of course 

 all such statements are empirical and have their limits : 

 but it is important that they are possible. 1 



It has been the chief result of comparative embryology 

 to show that the type as such is more clearly expressed in 

 developmental stages than it is in the adults, and that there- 

 fore the embryological stages of different groups may be very 

 much more similar to each other than are the adults : 

 that is the truth contained in the so-called " biogenetisches 

 Grundgesetz." But the specific differences of the species 

 are not wanting in any case of ontogeny, in spite of such 

 similarities in different groups during development. 



We have applied the name " systematics " or, if rationality 

 is excluded, " classification ' to all that part of a science 

 which deals with diversities instead of generalities : in such 

 a wide meaning systematics, of course, is not to be confused 

 with that which is commonly called so in biology, and 

 which describes only the exterior differences of form. 



1 Recent years have created the beginnings of a systematics based on 

 chemical differences of metabolism and its products : such differences in 

 fact have been found to go hand in hand with diversities of the type in 

 some cases (v. Bunge, Przibram, etc.). 



