UN Ee ee ee a ae 
1894.] Neo-Lamarckism and Neo-Darwinism. 669 
attacks upon Neo-Darwinism are unanswerable in any rational 
manner, and it is certain that they have forced Weismann into 
a change of position with reference to some of his definitions. 
Certain phases of this discussion appeal with particular force, 
of course, to some minds, while they exert little influence upon 
others. My own objections to Neo-Darwinism—and I admit 
that my bias is strong against it—seem to be somewhat differ- 
ent from those most commonly urged in opposition to it; and 
the three which chiefly influence me I shall present very 
briefly. 
1. I cannot see that the non-transmissibility of acquired 
characters is a necessary assumption to Weismann’s funda- 
mental arguments. I have already explained his reasoning 
from the reproduction of the one-celled organism. I cannot 
attempt any opinion of the probable facts upon which the hy- 
pothesis is founded. It may be said, in passing, that one of 
the prominent objections to the fundamental basis of the the- 
ory is the difficulty of deriving the mortal soma-plasm from 
the immortal germ-plasm, a question to which, however, Weis- 
mann has made a somewhat full reply. 
When organisms became complex, it was necessary to assume 
either that the soma-plasm does or does not directly influence 
the germ-plasm. Weismann discarded the various hypotheses 
which suppose that there is a vital and necessary connection be- 
tween the body units and reproductive units, and then to avoid 
the difficulties which the hereditability of acquired characters 
would entail, he supposed that such characters are not heredi- 
tary. His subsequent labors have been largely employed in 
trying to show that they are not. This supposition was made 
for the purpose of simplifying the hypothesis by removing the 
cumbrous gemmules of Darwin and the similar bodies or move- 
ments of other philosophers, and therefore by localizing the 
seat of the germ-plasm. But he immediately encounters diffi- 
culties quite as great as those which he avoids. In cases where 
there are alternate generations of asexual and sexual organ- 
isms, he must suppose that the germ-plasm is united with the 
soma-plasm, and is probably, therefore, distributed throughout 
the body. “There may be in fact cases,” Weismann writes, 
