
86 The American Naturalist. [January. 
under a delusion. The way in which they have placed themselves 
upon record shows that they have not reckoned with the consequences 
of their reckless speculations. 
In the first place, the supposition of a germ-plasma distinct from 
the plasma of the parent-body is a needless interjection into the 
machinery of hypothesis of biological evolution. It does not make 
the matter one whit clearer to suppose that the germ-plasma is neces- 
sary, than to suppose that aX of the living plasma of any and every dis- 
tinct species ts an idioplasm, or ts specific in so far as that species is con- 
cerned. If we now suppose, as a consequence of the action of the 
principle of physiological division of labor, first propounded by H. 
Milne-Edwards, that aX the plasma, or the whole of the specific proto- 
plasm or idioplasm of the organism, becomes physiologically differentiated 
and incapable of undergoing embryonic development, except that of the 
germ-cells or germinal plasma, as long ago urged by Professor Huxley, 
we get the same result as that reached by Weismann without involving 
ourselves in the consequences which beset his hypothesis, Zhis germ- 
inal matter is the only functionless and idle plasma in the parent body, 
capable of growing and consequently of multiplying its cellular units — 
within the parental organism at the expense of the surplus metabolism 
of the latter as a whole. Moreover, the germinal cells are alone 
capable of detaching themselves, or being detached, from the parental 
organism as products of over-nutrition, which have become useless to 
the life of the parent, as assumed in my preliminary paper ‘‘On the 
origin and meaning of sex.” This recognizes the apparent fact of 
the sétting aside or isolation of the germ-plasma, but does not make 
that fact the cause of the stability of species through the continuity of 
processes of growth, and the assumed but not empirically demonstrated 
isolation of such germ-plasma. My interpretation is in absolute 
accord with the requirements of the principles of modern physiology. , 
while the hypothesis of Weismann and his followers is in conflict with — 
those principles, and ultimately, as a necessary consequence, with the — 
still more comprehensive principle of the conservation of energy- 
Modern physiology, as well as the doctrine of the conservation of 
energy, positively forbids us to interpose any barrier between the 
plasma of the parent-body and that of the germ-cells, as is done by 
the promulgators of the hypothesis of the continuity and isolation of 
the germ-plasma. To do so robs us of the possibility of appealing to 
the agency of the workings of metabolism as the efficient causes of the 
modification of the germinal matter. Since metabolism, and all that 
‘it implies, is the only agent to which, according to modern physiology» 
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