432 The American Naturalist. [May, 
is necessary to state clearly that there is practically conclusive 
evidence for such a principle, not only in the later stages of 
development, as in the respiratory metamorphoses of the Am- 
phibia, but extending back to very much earlier stages than 
we have hitherto suspected. Thus a vast amount of evidence 
which has been brought forward as proof of Buffon’s factor, i. 
e., of the direct action of environment in producing definite 
and adaptive ontogenic variations is in reality in many cases 
no proof at all. 
Having thus eliminated errors of interpretation, the great 
question still remains as to what happens when the environ- 
ment is a wholly new one in the historical experience of the 
organism. Do the ontogenic variations exhibit a new direc- 
tion? Is this direction adaptive, 1, e., towards progressive 
adaptation? What relations have such new conditions to the 
hereditary potencies of the germ-cells? 
Out of all actual researches it becomes clear that experi- 
mentation can henceforth be separately directed upon the four 
stages of development, and that it will be possible in some 
degree to draw such lines of separation. New mechanical and 
chemical influences can be applied in each stage and with- 
drawn in the subsequent stages, the difficulty being to reach 
the extreme point where a profound influence is exerted with- 
out interfering with the reproductive function. 
One effect of new environment upon the gonagenic, gamo- 
genic, and embryogenic stages will be saltation. Ryder” has 
recently treated this in a most suggestive manner in discussing 
the origin of Japanese gold-fish. Turning to St. Hilaire’s hy- 
pothesis, we find he had in mind embryogenic saltation mainly 
traceable to respiratory and chemical changes. Virchow ex- 
tends the cause of sudden change further back to chemico- 
physical influences upon 0 germ-cells. The causes and 
modes of sudden d g from whatever ontogenic 
stage demand the most careful investigation, chiefly in their 
bearing upon the relation of ontogenic to phylogenic variation. 
"The inheritance of modifications due to disturbance of the early “en of de- 
velopment, especially in the To domesticated races of gold-carp. Proc. 
Acad. Nat. Sc. Phila., 1893, p. 7 ; 
