1910] . CURRENT LITERATURE 157 
Theory of individual development.—In a Darwin Anniversary address given 
at the University of Chicago and now published,?° Lituie analyzes organic devel- 
opment and the theories relating to it in an unusually clear and satisfactory way. 
He calls attention to the fact that ontogeny and phylogeny are not two separate 
and distinct series of phenomena, and that individual development is not some- 
thing distinct from evolution, but is a part of the process of evolution. In fact, 
we have no actual experience of any other form of development than individual 
development, racial development being an inference from innumerable facts. 
The development of the individual is a series of processes, capable of resolution 
into simpler biological processes, and these presumably into physico-chemical 
events. Such attempted analyses come under the head of physiology of develop- 
ment, a method of attack known in Germany as developmental mechanics. Under 
this head the author discusses embryonic primordia and the law of genetic restric- 
tion, the principle of organization, the rdle of cell division in development, and 
environment. 
The presentation of the last topic is especially suggestive, both extra-organic 
and intra-organic environment being recognized. e former needs no definition; 
the latter may be defined by the statement that each part of a developing embryo 
has an environment consisting of all the other parts, some of which constitute 
relatively immediate environmental factors, others relatively remote ones. Exam- 
ples of experiments are given to illustrate the influence of intra-organic environ- 
ment on development, which also show that an immense part of what is called 
inheritance is inheritance of environment only, that is, repetition of similar devel- 
opmental processes under similar conditions. It is stated that we are driven to 
the conclusion that the apparent simplicity of the germ is real; that the germ 
contains no gemmules, or determinants, or other representative particles; that 
development is truly epigenetic, a natural series of events that succeed one another 
according to physico-chemical and physiological laws; and that the explanation 
of the sequence consists simply in the discovery of each of its steps. 
The author discusses certain applications of this point of view, and shows 
that such biological conceptions as the inheritance of acquired characters, atavism, 
and unit characters are inconsistent with it, special attention being given to the 
last because it is essentially modern and has many adherents. The analysis of 
the term “character” is very effective, the term having been prescribed by taxono- 
mists and meaning any definable feature of an anatomical kind that differentiates 
Species. The study of the physiology of development shows that whatever else 
“characters” may be, they are not units; “they simply represent the sum of all 
Physiological processes coming to expression in definable areas or ways.” Charac- 
ter is essentially a static morphological term; in the study of heredity and devel- 
opment we are dealing with biological processes. 
The general conclusion is that the theory of individual development must 
neta 
*° Littie, Frank R., The theory of individual development. Popular — 
Monthly 75:2239-252. 1909. 
