1893.] Recent Literature. 549 
feathers be originated? Effort then, if it can be shown to have any 
creative power, must be relegated to a very special field, and cannot 
be considered as the sole or even principal originator of the fittest.” 
The above paragraph indicates a radical misconception of the 
proposition. 
Effort is simply the conscious preliminary to motion, and motion is 
the fundamental efficient cause of the leading modifications of 
structure. No knowledge or intention as to the result or effect (final 
cause) of the motion is to be supposed. It is motion which changes 
the environment of an animal, and which is thus at the bottom of 
whatever results from that change, let the immediate efficient agency 
be physical, chemical or mechanical. The psychic cause of this effort 
isa sensation. Of course in purely reflex acts, effort (which is assumed . 
to be conscious by its definition), is wanting, but the hypothesis 
sustained in the work quoted by Mr. Keeler, (The Origin of the 
Fittest), is that reflex acts have had their origin in conscious acts, 
and are the result of automatization, which is the ordinary process of 
education. Reflex motions then have had their origin in effort as 
well as the so-called voluntary acts, but at an earlier period. For 
this reason they have relatively little to do with the molar move- 
ments of animals at the present time, and therefore little to do with 
the present origin of specific characters. It is present effort which 
precedes most of the motions of animals, and which thus has everything 
to do with the environment, to which evolutionists of all shades appeal 
as an efficient cause. es 
The most important contribution towards the discovery of the origin 
of colors in birds by Mr. Keeler, is his demonstration of the law of the 
Assortment of Pigments. His classification of our birds in accordance 
with their color relations, is a valuable preliminary to further research. 
‘When we reach the final stage of the subject, the origin of the tints 
themselves, no definite progress is made in the book before us. As one 
of the most difficult problems in organic molecular physics, it requires a 
very special mode of experimental treatment, and one which Mr. 
Keeler has not attempted. The origin of color patterns is less difficult 
of approach, and some progress has been made in this direction, but 
the subject is yet in a very primitive stage. i 
The illustrations of the book are numerous and often in colors, and 
they add greatly toits value. The work is gotten up ın excellent 
style, and is a credit to all concerned in its publication. 
