NEOLAMARCKISM 417 
In his essay ‘‘On Dynamic Influences in Evolu- 
tion’’ W. H. Dall* holds the view that— 
*“ The environment stands in a relation to the in- 
dividual such as the hammer and anvil bear to the 
blacksmith’s hot iron. The organism suffers during 
its entire existence a continuous series of mechani- 
cal impacts, none the less real because invisible, or 
disguised by the fact that some of them are precipi- 
tated by voluntary effort of the individual itself. 
. . . Itis probable that since the initiation of life 
upon the planet no two organisms have ever been 
subjected to exactly the same dynamic influences 
durine their development, .. =. The reactions 
of the organism against the physical forces and 
mechanical properties of its environment are abun- 
dantly sufficient, if we are granted a single organism, 
with a tendency to grow, to begin with; time for 
the operation of the forces; and the principle of the 
survival of the fittest.”’ 
In his paper on the hinge of Pelecypod molluscs 
and its development, he has pointed out a number 
of the particular ways in which the dynamics of the 
environment may act on the characters of the hinge 
and shell of bivalve molluscs. He has also shown 
that the initiation and development of the columel- 
lar plaits in Voluta, Mitra, and other gastropod mol- 
luscs ‘‘ are the necessary mechanical result of certain 
comparatively simple physical conditions; and that 
the variations and peculiarities connected with these 
plaits perfectly harmonize with the results which fol- 
low within organic material subjected to analogous 
stresses.’” 
* Proceedings Biological Society of Washington, 1890, 
27 
