286 The New Factor in Organic Development . [May, 
of the phenomena which Darwin groups together under the 
principle “ Economy of Growth,” than can be obtained by 
referring them to natural selection. 
The organs engage in conflict also for nutriment. Goethe 
and Geoffroy St. Hilaire admitted this principle in their law 
of the “compensation of growth,” which declares that when 
an excess of nutriment is required for building up any 
particular part, others are more scantily nourished, and are 
thus reduced in size. Darwin scarcely, gives this law due 
recognition. 
In summing up the results of this internal contest, the 
author makes use of a happy illustration. To deduce all 
advantageous properties of an organism from the results of 
direCt selection in the struggle for existence with other 
individuals and with the outer world, is as great an error 
as would be committed by a sociologist or philosophical 
historian who should attempt to explain all the arrange- 
ments of a state in legislation, executive administration, 
science, art, commerce, and manufactures, from the effects 
of wars with neighbouring powers. 
We have thus given a very meagre outline of a new 
fadtor in organic evolution. The idea of Dr. Roux seems 
to us to deserve most careful experimental investigation. 
Its true value can only be learnt from its aCtual application 
to some of the many unsolved problems with which the 
followers of Darwin and Wallace have so far contended 
with doubtful success. We do not suppose, nor does Dr. 
Roux for a moment insinuate, that the struggle within the 
organism, the conflict of parts, is the one and only considera- 
tion necessary to supplement natural selection. But we 
believe that it will be found of great service, and that it will 
prove especially efficient in explaining many of those minute 
delicate contrivances and cases of purposiveness upon which 
the advocates of individual creation still take their stand 
and upon which selection throws no clear light. 
It may here be asked without for one moment seeking to 
undervalue the immense services which Darwin and 
Wallace have rendered to Science, whether evolutionists are 
not returning to a position more like that of Lamarck ? 
Natural selection is no longer all in all. It requires the aid 
of the principle of use and disuse, of the influence of the 
external medium as analysed by Semper and, as we now see, 
of the internal conflict of Dr. Roux. Perhaps other agents 
which take part in the development of the organic world 
may yet be discovered, and may enable biologists to deal 
satisfactorily with the serious doubts which yet beset the 
question. 
