Chap. XXI. 
AND CONCLUDING EEMABKS. 
389 
but breeds from all the superior and neglects all the 
inferior individuals. He thus slowly but surely modi- 
fies his stock, and unconsciously forms a new strain. 
So with respect to modifications, acquired indepen- 
dently of selection, and due to variations arising from 
the nature of the organism and the action of the sur- 
rounding conditions, or from changed habits of life, no 
single pair will have been modified in a much greater 
de gree than the other pairs which inhabit the same 
Country, for all will have been continually blended 
through free intercrossing. 
By considering the embryological structure of man, 
- — the homologies which he presents with the lower 
animals, — the rudiments which he retains, — and the 
reversions to which he is liable, we can partly recall 
in imagination the former condition of our early pro- 
genitors ; and can approximately place them in their 
proper position in the zoological series. We thus learn 
that man is descended from a hairy quadruped, fur- 
nished with a tail and pointed ears, probably arboreal 
in its habits, and an inhabitant of the Old World. 
This creature, if its whole structure had been examined 
by a naturalist, would have been classed amongst the 
Quadrumana, as surely as would the common and still 
more ancient progenitor of the Old and New World 
monkeys. The Quadrumana and all the higher mam- 
mals are probably derived from an ancient marsupial 
animal, and this through a Jong line of diversified 
forms, either from some reptile-like or some amphibian- 
i'ke creature, and this again from some fish-like animal. 
b> the dim obscurity of the past we can see that the 
oarly progenitor of all the Vertebrata must have been 
a n aquatic animal, provided with branchiae, witli the two 
^ e xes united in the same individual, and with the most 
'niportant organs of the body (such as the brain and 
