Xt PHENOMENA OF ORGANIC NATURE 455 
is to a worm, ora 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, 
