242 ENTOMOLOGY 
periments upon the subject have given decidedly negative 
results. Thus Weismann found that the amputation of the 
tails of hundreds of mice, down to the nineteenth generation, 
had no influence on the tails of the descendants. 
Mechanical injuries to the body of an organism are merely 
casual, or accidental, effects of the environment and appear to 
have no influence upon the germ cells. From the standpoint 
of adaptation, injuries are only of minor importance. 
Functional Variations.—While it is certain that the use 
or disuse of organs affects their form in the individual, it 
remains doubtful whether the effects of use and disuse are 
transmissible. Weismann and his followers contend that they 
are not. On the other hand, Neo-Lamarckians, as Cope, 
Hyatt, H. F. Osborn, Packard and Eimer, have maintained 
that they are. Weismann admits, however, that both use and 
disuse may lead indirectly to variations, “the former when- 
ever an increase as regards the character concerned is useful, 
and the latter in all cases in which an organ is no longer of 
any importance in the preservation of the species’; and that 
these variations may be acted upon by natural selection. 
Thus, in a few words, the question stands. 
Environmental Variations.—Under this head may be 
classed such variations as are due directly to climate, nutrition 
and other primary environmental influences. It is certain 
that changes of temperature, light, and food, for example, 
cause corresponding changes of form and function in the indi- 
vidual organism; though the inheritance of these changes 
directly induced by the environment is the subject of much 
debate. 
Dallinger took flagellate infusorians that at first would die 
at a temperature of 23° C., and by slowly raising the tempera- 
ture through several years, brought them safely to a tempera- 
ture of 70° C. There was some mortality, to be sure, in his 
experiments, but other experimenters have obtained similar 
results without the loss of a single individual, and therefore— 
it is important to note—without the entrance of natural selec- 
