Embryology. 99 
in the life-history of existing deer. Or, in other 
words, the antlers of an existing deer furnish in their 
development a kind of résumé, or recapitulation, of the 
successive phases whereby the primitive horn was grad- 
ually superseded by horns presenting a greater and 
greater numberof prongs in successive species of extinct 
deer (Fig. 26). Nowit must be obvious that such a re- 
capitulation in the life-history of an existing animal of 
developmental changes successively distinctive of sundry 
allied, though now extinct species, speaks strongly in 
favour of evolution. For as it is of the essence of this 
theory that new forms arise from older forms by way 
of hereditary descent, we should antecedently expect, 
if the theory is true, that the phases of development 
presented by the individual organism would follow, in 
their main outlines, those phases of development 
through which their long line of ancestors had passed. 
The only alternative view is that as species of deer, 
for instance, were separately created, additional prongs 
were successively added to their antlers; and yet 
that, in order to be so added to successive species, 
every individual deer belonging to later species was 
required to repeat in his own lifetime the process of 
successive additions which had previously taken 
place in a remote series of extinct species. Now I 
do not deny that this view is a possible view; but I 
do deny that it is a probable one. According to 
the evolutionary interpretation of such facts, we can 
see a very good reason why the life-history of the 
individual is thus a condensed résumé of the life- 
history of its ancestral species. But according to the 
opposite view no reason can be assigned why such 
should be the case. In a previous chapter—the 
H 2 
