3582 The Zoologist— July, 1873. 



habits, that their offspring resembled them, and that there was a 

 community of blood-relationship between them. Thus a rough 

 idea of species is arrived at; but when scientific men have tried to 

 define the limits of these different species there has arisen the 

 greatest difficulty, each definition generally depending upon what 

 the arranger really believed to be the origin of species, and there- 

 fore impossible to be used in discussing the origin of species 

 without begging the question. 



Now as a merely useful word, and not a dogmatic one, I think 

 "species" may be used in two ways; the first, I suppose, would 

 be the logical one, that it was the lowest or simplest unit of 

 generalization — i. e. that all animals so nearly alike that they 

 cannot conveniently be divided into smaller groups should be con- 

 sidered as belonging to the same species. The second requires a 

 little elucidation : all animals between which there is a community 

 of blood amalgamation are not exactly alike, although more or less 

 similar, and minor differences amongst animals having such com- 

 munity are sometimes capable of generalization ; still this blood- 

 relationship seems to be the central fact around which all aflSnities 

 of form, habit, or character group themselves; and there is no 

 dispute or doubt at all that where a certain amount of divergence 

 in these affinities or resemblances is found, there is no longer any 

 possibility of amalgamation. 



Now a definition framed on this fact will suit very well for the 

 purposes of this discussion, and is included in the first explanation. 

 That is, the simplest unit of generalization is that all those animals 

 amongst whom there is the possibility of blood amalgamation shall 

 be considered to be of the same species, and where there is no such 

 possibility then such animals are to be considered as belonging to 

 different species. ^ 



It is to be distinctly understood I do not in any way wish to 

 beg the question as to whether this is a correct definition of the 

 term species, when used zoologically : that would be settling the 

 whole matter at once. But that as every one, orthodox naturalists, 

 Darwinists, or common-sense observers, arc all agreed in the fact 

 that there is such a limit, I take that limit for convenience as the 

 definition of the word as I use it here. 



The number of different species of animals in the world is 

 immense, infinite, to the ordinary mind, and it might occur on first 

 thoughts that however these different forms of life originated they 



