1010 . The American Naturalist. [December, 
reason why it should not exercise this right in the case of the 
term ‘acquired.’ ” 
“Tt is certainly necessary to have two terms which distin- 
guish sharply between the two chief groups of characters—the 
primary characters which first appear in the body itself, and 
the secondary ones which owe their appearance to variations 
in the germ, however such variations may have arisen.” 
He calls the former acquired or “somatogenic,” and the 
latter “ blastogenic,” and maintains that “the somatogenie char- 
acters cannot be transmitted,” or, rather, that “those who 
assert that they can be transmitted must furnish the requisite 
proofs.” “The somatogenic characters not only include the 
effects of mutilation, but the changes which follow from 
increased or diminished performance of function, and those 
which are directly due to nutrition and any of the other 
external inflences which act upon the body.”® 
Here, then, we have Prof. Weismann’s definition of acquired 
characters which are not transmitted, and it would seem to be 
sufficiently definite. Now, note the process of contraction. 
Speaking of the source of the variation in the germ, he says: 
“I believe, however, that they (the variations) can be 
referred to the various external influences to which the germ 
is exposed before the commencement of embryonic develop- 
ment. Hence we may fairly attribute to the adult organism 
influences which determine the phyletic development of its 
descendants. For the germ cells are contained in the organ 
aah 
= ieee eS 
T 
ism, and the external influences which affect them are inti- — 
mately connected with the state of the organism in which 
they lie hid.” * “en 
Professor Weismann, by the way, concedes that a quantitative 
variation of the germ is thus brought about. “I must confess — 
*Essays upon Heredity, August Weismann, Page 425. 
3According to this definition, the increased toleration of a high temperature, 
shown by the bacteriain Dr. Dallinger’s experiments, would be an acquired engin l 
and that this character was transmitted was experimentally proven. 
In the discus 
sion of the paper, however, Prof. Morse claimed that the toleration of unon" i 
temperature was due to matural selection, pure and simple, a position which it 15 BY 
purpose of this article to combat. A forcible illustration of the difficulty . : 
of in the following pages. 
‘Essays on Heredity, Weismann. Page 105. 
