338 READINGS IN EVOLUTION, GENETICS, AND EUGENICS 
they offer no difficulties because he can always iall back upon the 
statement that there is, among the lower forms at least, reserve germ 
plasm equally distributed over the whole body ready to differentiate 
into definite germ cells when needed. This type of appeal is abhor- 
rent to the physiologist, and with some justification, for it really 
begs the question by assuming that any cell that is capable of form- 
ing germ cells belongs to the more or less sacred lineage of germ plasm. 
If we confine the application of the germ-plasm idea to the higher 
animals, such as vertebrates and insects, we would obviate these chief 
objections, and the present writer would take the view that it is only 
among the upper ranges of highly specialized animals that the con- 
tinuity of the germ-plasm concept holds solidly. 
Another chief objection to the germ-plasm system has to do with 
the supposed insulation or apartness of the germ plasm. Physiolo- 
gists have found that there is an extremely intimate correlation in 
function between practically all parts of a living organism. Many 
of the structures, such as the rudimentary pituitary body, the thyroids, 
the adrenal body, and various other bodies whose function was long 
unknown, have now been shown to exercise a profound effect on the 
development of the whole body. Since practically all tissues are 
known to affect at least some other tissues, is it likely, the physiologist 
asks, that none of the other tissues affect the germinal tissues? The 
organism is to be viewed, it is said, not as a collection of independently 
functioning parts, but as a single coherent unit. On this view no 
tissue can be thought of as beyond the influence of organic changes. 
The classic argument of the Weismannians was that we can con- 
ceive of no mechanism by means of which somatic changes can be carried 
back into the germ cells, and therefore there is no such mechanism. 
Now the fallacy of this argument is obvious; even if we could con- 
ceive of no suitable mechanism for this purpose, this does not preclude 
the existence of such a mechanism. Moreover, according to Professor 
Guyer, just such a mechanism actually exists, as will be brought out in 
the following quotation from one of his recent publications.—Ep.] 
A POSSIBLE MECHANISM FOR THE TRANSMISSION OF 
ACQUIRED CHARACTERS! 
MICHAEL F. GUYER 
Some selectionists glibly assert that new characters arise as the 
result of spontaneous changes in the germ. What is meant by this? 
From M. F. Guyer, “Immune Sera and Certain Biological Problems,”’ 
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