39 
dimorphism in sphinx larvae, which has been shown by Poutron to be 
probably due to this factor. | 
The other paper was by Dr. ArnoLp Grar on “The Problem of the 
Transmission of Acquired Characters.” 
Dr. Gear discussed the views of the modern schools of evolutionists 
and adopted the view that the transmission of acquired characters must 
be admitted to occur. He cited several examples which seemed to support 
this view, and especially discussed the sucker in leeches as an adaptation 
to parasitism and the evolution of the chambered shell in a series of fossil 
Cephalopods. 
Professor OsBorn remarked in criticism of Dr. Grar’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 constitution. The Environment. If the en- 
vironment is normal the adult would 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. pro- 
found that in many cases it would appear as if the constitution, or stirp, 
had also changed. Illustrations might be given of changes of the most 
profound character induced by changes in either of the above factors of 
the environment, and in the case of the motor factor or animal motion, 
the habits of the animal might, in the course of a life time, profoundly 
modify its structure. For example, if the human infant were brought up 
in the branches of a tree as an arboreal type instead of as a terrestrial, 
bi-pedal type, there is little doubt that some of the well known early 
adaptations to arboreal habit (such as the turning in of the soles of the 
feet, and the grasping of the hands) might be retained and cultivated, 
thus a profoundly different type of man would be produced. Similar 
changes in the action of environment are constantly in progress in nature 
since there is no doubt that the changes of environment and the new 
habits which it so brings about far outstrip all changes in constitution. 
This fact which has not been sufficiently emphasized before, offers an 
explanation of the evidence advanced by Cork and other writers that change 
in the forms of the skeletons of the vertebrates first appears in ontogeny 
and subsequently in phylogeny. During the enormously long period of 
time in which habits induced ontogenic variations it is possible for natural 
selection to work very slowly and gradually upon predispositions to useful 
correlated variations, and thus what are primarily ontogenic variations 
become slowly apparent as phylogenic variations or congenital 
characters of the race. Man, for instance, has been upon the earth perhaps 
seventy thousand years; natural selection has been slowly operating upon 
certain of these predispositions, but has not yet eliminated those traces 
of the human arboreal habits, nor completely adapted the human frame 
to the upright position. This is as much an expression of habit and onto- 
genic variation as it is a constitutional character. Very similar views 
were expressed to the speaker in a conversation recently held with Pro- 
fessor Lioyp Morean, and it appears as if a similar conclusion had been 
arrived at independently. Professor Morgan believed that this explanation 
