194 The American Naturalist. [ March, 
demonstration of how evolution works upon their basis as to be 
conclusive; nor will either side admit the value of the evidence 
furnished by the other. Contrast two of our most vigorous writers 
on this point :? 
“ This is all the more necessary, in that this author (Weismann) 
and his followers repudiate the evidence upon which the claim is 
made that acquired characters, taken in the widest Lamarckian 
sense, can be transmitted. During a period extending over fifteen 
years, the present writer has devoted himself to a study of the 
genesis of adaptations, and with the lapse of time the conviction has 
grown only the clearer that these authors are laboring undera 
delusion. The way in which they have placed themselves upon 
record shows that they have not reckoned with the consequences 
of their reckless speculations.” 
A few segue later Tes echoing Weismann, * writes to 
Nature : 
“ Naturalists are at ect interested in the attempt to decide 
_ whether Lamarck was justified in his statement that acquired 
characters are transmitted from the parents so changed to their off 
spring. Many of us hold that he was not; since, however plausi- 
ble his laws above quoted may appear, it has not been possible to 
bring forward a single case in which the acquisition of a character 
as described by Lamarck and its subsequent transmission to off 
spring have been conclusively observed. We consider that, until 
such cases can be adduced, it is not legitimate to assume the truth 
of Lamarck’s second law.” 
Nature of the Discussion—Before taking up the question of 
evidence as to this factor in evolution, let us clearly understand 
what we are not discussing at the present time. First, the law of 
natural selection is well established and no longer-under discus- 
sion; it furnishes, by far the best, in fact the only, explanation 
which can be offered for many adaptations,—the question before us 
"Ryder. “A Physiological Hypothesis of Heredity and Variation.” AM. NATUR- 
ALIST, Jan., 1890, p. 85. : 
3" There are no observations which prove the transmission of functional atrophy % 
hy, and it is hardly to be expected that we shall obtain proofs in the 
