ECOLOGY AND BIOLOGY 317 
thirdly of specificity of behavior, and fourthly of structural characters 
modifying behavior. Relatively fixed taxonomic integumentary charac- 
ters have no bearing on ecological matters, not even according to the 
broadest definitions of the subject. The characters which are not related 
to the environment and which are of no ecological value are the ones 
quite generally used in breeding work, specificity of behavior standing 
second, and plastic structure third, primary ecological matters usually 
receiving no adequate attention or only such attention as comes incidentally 
with the handling of the material. The results consist of noted differences 
in reaction to light of doubtful intensity and quality, or similar inaccu- 
rately measured temperature differences, etc. The testing of primary 
ecological characters can be easily conducted and will answer the question 
before us. 
With all of its imperfections and uncertainties, the ideas of phylogeny 
which are presented in our phylogenetic system of taxonomy are an impor- 
tant asset in zodlogical thinking from the point of view of structure and 
development. The classification which ecologists are striving to build 
up will serve a purpose in behavior, physiology, and ecology, analogous 
in this respect to that served by the phylogenetic classification in morpho- 
logical thought, but should be flexible rather than rigid and true to fact 
rather than to schemes. Figuratively speaking, an ecological classifica- 
tion cuts taxonomy vertically, showing many structural adaptations as 
matters of stratum or over-adaptations (205) or lack of adjustment to 
conditions (206, 206a). It also cuts it again horizontally, showing eco- 
logical similarity in organisms structurally and phylogenetically diverse. 
It therefore provides a new and different means of organization of data. 
In this work we have sharply separated evolution and structure, 
on the one hand, from physiology and behavior, on the other. Space, 
clearness, and the condition of the subjects have forbidden that we 
attempt to unite them here. While it may be expedient to continue in 
this manner until our knowledge of physiology and behavior is commen- 
surate with that of the other subjects, the following of such a course 
indefinitely, with respect to either morphological or physiological aspects 
of biology, cannot, if it be general, bring about the best development or 
unification of biological science. Indeed, its present lack of unity is 
traceable to such a course followed until recently by zodlogists generally. 
If our understanding of the data of physiological cytology be correct, 
we may expect to find so-called structures of some sort within or among 
the cells concerned in function, which stand for or are correlated with 
each physiological state and physiological condition to which we have 
