XI PHENOMENA OF ORGANIC NATURE 455 



is to a worm, or a snail, or any member of the other 

 sub-kingdoms. For similar reasons men and horses 

 are arranged as members of the same Class, Mam- 

 malia; men and apes as members of the same 

 Order, Primates ; and if there were any animals 

 more like men than they were like any of the 

 apes, and yet different from men in important and 

 constant particulars of their organisation, we should 

 rank them as members of the same Family, or of 

 the same Genus, but as of distinct Species. 



That it is possible to arrange all the varied 

 forms of animals into groups, having this sort of 

 singular subordination one to the other, is a very 

 remarkable circumstance ; but, as Mr. Darwin re- 

 marks, this is a result which is quite to be ex- 

 pected, if the principles which he lays down be 

 correct. Take the case of the races which are 

 known to be produced by the operation of atavism 

 and variability, and the conditions of existence 

 which check and modify these tendencies. Take 

 the case of the pigeons that I brought before you : 

 there it was shown that they might be all classed 

 as belonging to some one of five principal divi- 

 sions, and that within these divisions other sub- 

 ordinate groups might be formed. The members 

 of these groups are related to one another in just 

 the same way as the genera of a family, and the 

 groups themselves as the families of an order, or 

 the orders of a class ; while all have the same sort 

 of structural relations with the wild rock-pigeon, 



58 



