78 Evolution and Adaptation 
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.” 
Hurst concludes: “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.” The case 
of the appendix in man might have been cited here as 
acase in point. It is supposed to have been larger in the 
ancestors of man, but we do not find it appearing full size in 
the embryo and later becoming rudimentary. The preceding 
statements willshow that, while Hurst’s view is similar in some 
respects to my own, yet it differs in one fundamental respect 
from it, and in this regard he approaches more nearly to the 
theory of Von Baer. 
Hertwig has recently raised some new points of issue in 
regard to the recapitulation theory, and since he.may appear 
to have penetrated farther than most other embryologists of 
the present time, it will be necessary to examine his view 
somewhat carefully. He speaks of the germ-cell (egg, or 
spermatozoén) as a species-cell, because it contains, in its 
finer organization, the essential features of the species to 
which it belongs. There are as many of these kinds of cells 
as there are different kinds of animals and plants. Since the 
bodies of the higher animals have developed from these 
species-cells, so the latter must have passed in their phylogeny 
through a corresponding development from a simple to a 
more and more complex cell-structure. ‘Our doctrine is, 
that the species-cell, even as the adult, many-celled representa- 
tive of the species, has passed through a progressive, and, 
indeed, in general a corresponding development in the course 
