JULY 2, 1897]. 
helpful to the student. We take pleasure in 
commending the work to nature lovers, and 
particularly to the large and healthful class of 
of out-door students of birds. 
Cc. H. M. 
The Present Evolution of Man. By. G. ARCH- 
DALL REID. London, Chapman and Hall. 
1896. pp. 370. 
The work which has appeared with the above 
title consists in fact of two parts; up to p. 196 
it has reference to organic evolution in general, 
and only the remaining portion, pp. 197-370, 
treats especially of the evolution of man. In 
the earlier part of the work there is given a 
very excellent discussion of the broad principles 
of evolution, and particularly of the reasons 
which lead to the conclusion that acquired char- 
acters are not inherited by other than the low- 
est organisms. The argument against the 
transmission of acquired characters, as ordi- 
narily understood, appears to the writer conclu- 
sive, and he would commend it to the neo-La- 
marckians for dissection. It is also well shown 
that under ordinary circumstances natural se- 
lection works upon normal variations, and not 
upon those which occur only at infrequent in- 
tervals. Much stress is also laid, very justly, 
upon the importance of characters which are 
normally acquired, and of the power of acquir- 
ing them. 
An interesting argument runs as follows: In- 
asmuch as progressive or new variations may be 
in all directions, but atavistic variations are in 
one direction—towards the ancestry—there will 
be a tendency, in the long run, in the absence of 
selection, to revert to a more primitive condi- 
tion, owing to the dominance of the atavistic 
variations. When the evolution has been very 
slow, as with certain Brachiopoda, the rever- 
sion will be scarcely noticeable, but when it has 
been very rapid, as with many domesticated 
animals, the reversion will be rapid and striking. 
All this appears to accord with the known facts, 
but to the present writer it seems an inadequate 
statement of the actual course of events. Mr. 
Reid says: ‘‘ In every species natural selection 
as a cause of evolution, and atavism as a cause 
of retrogression, are constantly at war.’’ It 
does not seem to me that this is necessarily the 
SCIENCE. 
33 
case, but that, on the other hand, atavistic 
variations may be themselves selected. The 
germ, it must be supposed, contains units 
representing many phases of existence, some of 
which have been held over, undeveloped, 
through many generations, while others are 
new. When one of the latter develops we say 
the variation is a progressive one; when the 
former develop we call the result atavism. It 
is reasonable to suppose that environmental and 
germinal selection are the factors which deter- 
mine which of its possible developments the 
germ shall undergo. That is to say, there are 
two factors involved, one the relative vitality 
or growth-force of the several germinal ele- 
ments, the other the environment favoring one 
or the other in their struggle This same strug- 
gle, in various phases, goes on through life; for 
example, many people have two or more talents, 
which cannot be fully exercised simultaneously; 
other things being equal, the strongest will pre- 
vail, but how often the environment steps in 
and dictates which of the possible paths of life 
shall be followed. 
This being made clear, it is evident that 
atavism increases the range of possibilities of 
any given germ, and thus may be highly advan- 
tageous. Especially is this the case when the 
environment is changeable, as with seasonally 
dimorphic butterflies, one phase of which is 
probably in most cases older than the other. 
My own studies of bees have led me to believe 
that many of the specific characters had their 
origin in atavistic variations, because it often 
happens that a character will appear in two 
different groups independently, and yet be so 
striking and definite as to suggest that it must 
have existed in a common ancestor, though not 
in the immediate ones. 
How, then, as to atavism in the absence of 
selection? It is perfectly obvious that any 
given adult individual does not, under existing 
circumstances, represent the average potential, 
if one may so express it, of its race. In the 
first place, the individual is probably a survivor 
out of many—has been the subject of natural 
selection. In the second, it represents only 
one (selected) phase of the many that were pos- 
sible to the germ. In the total absence of se- 
lection (an impossible thing) we should obviously 
