198 NATURAL SCIENCE. Marcu, 
one. If the variation is a mere increase in the definitive size of an 
organ which has hitherto not only increased in size in the evolution 
of the species, but also has gyown during development of the individual, 
then, of course, a variation affecting the rudiment of this organ at all 
stages of development in which it is present, and causing it to grow 
more rapidly, will render the late stages of development (as far as 
that organ is concerned) more like the adult stage of the ancestor. 
This, however, is a mere result of the mode of growth of the 
particular organ ; its smaller size in late embryonic stages than in the 
adult is not a result, still less is it a ‘record’ of the course of 
evolution. 
The antlers of stags will serve as an example. Each stag 
develops a new pair of antlers in each successive year, and each pair 
of antlers is larger than the pair produced in the previous year. 
This yearly increase in the size of the antlers has been put forward 
as an example of an ontogenetic record of past evolution. I, however, 
deny that it is such a record. The series of ancestors may have 
possessed larger antlers in each generation than in the generation 
before it. It is not an occasional accidental parallelism between the 
ontogeny and the phylogeny which I deny, but the causal relation 
between the two. Had the ancestors had larger antlers than the 
existing ones, there is no justification for the assumption that existing 
stags would acquire antlers of which each pair, in later years, would 
be smaller than those of the previous year. The yearly increase in 
the size of the antlers is itself a character determined by Natural 
Selection. Phylogeny appears to have run parallel with the pre-existing 
Ontogeny. There are many breeds of hornless sheep, but they do not 
bear large horns in early years and then shed them. If a rudiment 
ever appears in the embryo of such sheep, its growth is very early 
arrested. 
So it is in all the alleged cases of recapitulation. The gill-arches 
and clefts, and the blood-vessels of an embryo bird or mammal, 
present that striking resemblance to the corresponding parts of the 
embryo of a fish which is expressed in Von Baer’s law. They differ, 
perhaps, only very slightly indeed. They are the modified repre- 
sentatives of the embryonic structures of a common ancestor. 
Whether they were, in that ancestor, the rudiments of gill-arches and 
clefts, &c., like those of an adult fish, or not, cannot be decided by 
embryological study. All we learn is that what now serve in their 
modified forms as the rudiments of the gill-arches ofa fish, and of 
certain parts about the throat of a bird or a mammal, are so similar in 
early stages of development as to show that these parts are homo- 
logous. The greater resemblance of them to the adult structures of 
a fish than to those of a mammal may Justify the belief that they 
served in a common ancestor as the rudiments of adult structures 
more like the adult structures of a fish than of a mammal, and that 
is all: they do not prove even that. 
