976 
have been set aside by biologists as crudely 
anthropomorphic. In reality the immedi- 
ate causes or mechanisms of evolution are 
as completely unknown as those of the 
other spontaneous or active properties of 
protoplasm. Until more light can be shed 
upon the physical and chemical how and 
why of assimilation, growth, irritability, 
motility and reproduction, we can scarcely 
expect to attain an adequate comprehen- 
sion of the process which represents a con- 
tinuous summary of these organic activi- 
ties. 
The center of activity or citadel of the 
protoplasm of cells is located, evidently, in 
the nucleus, and there are also reasons for 
believing that the number, position or other 
relations of the chromatin bands have im- 
portant functions in the processes of cell 
division, and possibly also in determining 
the relative preponderance of the parental 
influences. But such facts are very far 
from proving that either heredity, variation 
or the resultant evolutionary motion is con- 
trolled by purely cytological processes, or 
that there is any such thing as a ‘ hered- 
itary mechanism.’* Developed to their 
logical conclusions, theories of determinants 
coincide with Nageli’s attempted deduction 
of the organic universe from the chemical 
and physical structure of protoplasm, in ig- 
noring the fact that even in the highest or- 
ganisms cells are still cells, and that from 
the cytological standpoint they are not im- 
proved, but degraded by specialization. A 
complex organism is more than the com- 
ponent cells, and evolution is not only a 
cytological, but a social and supercellular 
*The well-known phenomena of asexual re- 
production, parthenogenesis and replacement of lost 
parts should have saved us from theories of localized 
and mechanical heredity, but if further proof is 
needed if is now available in the experiments of 
Loeb in artificial parthenogenesis, those of Delage 
and others with enucleated fragments of eggs, and 
those of Mr. A. J. Pieters in growing normal plants 
from pieces of cotyledons. 
SCIENCE. 
[N.S. Vou. XIII. No. 338. 
process. Life itself is the ‘unknown factor,’ 
or neglected cause, which vitiates the 
theories of those who expect a complete 
expression of organic phenomena in terms 
of current conceptions of matter and molec- 
ular and atomic forces. 
Under cytological or intracellular theo- 
ries the evolution of unicellular organisms 
must involve principles fundamentally dis- 
tinct from those required in multicellular 
groups, with a similar gap intervening 
when compound individuals and social 
units are being dealt with. But if we look 
upon evolution asa normal property of pro- 
toplasm no such complications need be met, 
higher acquirements being added by gradual 
superposition. In nature, moreover, there 
are no breaks in the chain which connects 
simple and complex types of individuality. 
Beginning with the absolute individuality 
of some unicellular organisms where each 
cell may compete directly with every other 
cell, we have all grades of association and 
adhesion ; also when the individual com- 
pacted of similar and equivalent cells is 
traced to the point where it begins to man- 
ifest increasing differentiation of parts into 
special tissues and organs. Equally perfect 
is the series of social adaptations and in- 
stincts, through simple aggregations or 
flocks, to the complex caste differentiations 
of the highly organized colonies of the social 
hymenoptera and termites. 
A general law of biological evolution must 
embrace the morphology, physiology, ecol- 
ogy, psychology, ethnology and sociology 
of the entire organic series, to say nothing 
of still more general or philosophical appli- 
cations. But while any process of gradual 
change and readjustment would bear the 
teleological interpretation of natural selec- 
tion, that theory does not furnish an ade- 
quate explanation or supply causal con- 
nection for the succession of phenomena 
encountered in any department of biolog- 
ical study. 
