1896. ] NEW YORK ACADEMY OF SCIENCES. 141 
So I think we can find no reason for believing that we have 
to do with a case of progressive modification, however much 
our varietal tree may suggest a genetic tree. It seems more 
probable to suppose that even the most extreme of these forms 
may hatch from the same batch of eggs. And here we have a 
beautiful example of the definite tendency of variation. Vari- 
ation must take place along certain lines predetermined by the 
nature of the organism. 
It is to be regretted that we have so few biological data in 
regard to this and allied species. Future explorations will per- 
haps yield these. 
ZOOLOGICAL LABORATORY, 
COLUMBIA UNIVERSITY, March, 1896. 
Prof. Osborn, in discussion, coincided with the view that the 
variation could not be explained by natural selection. Dr. Dyar, 
however, thought the explanation by natural selection not neces- 
sarily excluded, since the variations seemed analogous to the 
dimorphism in sphinx larve, which has been shown by Poulton 
to be probably due to this factor. 
The other paper was by Dr. Arnold Graf, on “ The Problem 
of the Transmission of Acquired Characters.” 
Dr. Graf discussed the views of the modern schools of evolu- 
tionists and adopted the view that the transmission of acquired 
characters must be admitted to occur. He cited several ex- 
amples which seemed to support this view, and especially dis- 
cussed the sucker in leeches as an adaptation to parasitism and 
the evolution of the chambered shell in a series of fossil Cepha- 
lopods. 
Professor Osborn remarked in criticism of Dr. Graf’s paper 
that this statement does not appear to recognize the distinction 
between ontogenic and phylogenic variation, or that the adult 
form of any organism is an exponent of the stirp, or consti- 
tution + the environment. If the environment is normal the 
adult will be normal, but if the environment (which includes 
all the atmospheric, chemical, nutritive, motor and psychical 
circumstances under which the animal is reared) were to change, 
the adult would change correspondingly ; and these changes 
would be so profound that in many cases it would appear as if 
