LEADING GROUPS OF EXISTING SYSTEMS 147 



most general relations of animals than Cuvier when he perceived, 

 not only that these primary groups are founded upon differences in 

 the plan of their structure, but also how they are essentially related 

 to one another. 



Though the term type is generally employed to designate the great 

 fundamental divisions of the animal kingdom, I shall not use it in 

 future, but prefer for it the term branch of the animal kingdom, 

 because the term type is employed in too many different acceptations, 

 and quite as commonly to designate any group of any kind or any 

 peculiar modification of structure stamped with a distinct and 

 marked character as to designate the primary divisions of the animal 

 kingdom. We speak, for instance, of specific types, generic types, 

 family types, ordinal types, classic types, and also of a typical struc- 

 ture. The use of the word type in this sense is so frequent on almost 

 every page of our systematic works, in Zoology and in treatises of 

 Comparative Anatomy, that it seems to me desirable, in order to 

 avoid every possible equivocation in the designation of the most im- 

 portant great primary divisions among animals, to call them branches 

 of the animal kingdom, rather than types. 



That, however, our systems are more true to nature than they are 

 often supposed to be seems to me to be proved by the gradual ap- 

 proximation of scientific men to each other in their results and in 

 the forms by which they express those results. The idea which lies at 

 the foundation of the great primary divisions of the animal kingdom 

 is the most general conception possible in connection with the plan 

 of a definite creation; these divisions are therefore the most compre- 

 hensive of all and properly take the lead in a natural classification, 

 as representing the first and broadest relations of the different natural 

 groups of the animal kingdom, the general formula which they each 

 obey. What we call branches expresses, in fact, a purely ideal con- 

 nection between animals, the intellectual conception which unites 

 them in the creative thought. It seems to me that the more we ex- 

 amine the true significance of this kind of group, the more we shall 

 be convinced that they are not founded upon material relations. The 

 lesser divisions which succeed next are founded upon special quali- 

 fications of the plan and differ one from the other by the character of 

 these qualifications. Should it be found that the features in the ani- 

 mal kingdom which, next to the plan of structure, extend over the 



