OUT 
and actions, and they perform acts which, however voluntary, and, as I 
believe, conscious, in many cases, as in that of our Yucca moth, could 
not be performed were the tendency not inherited. Every larva which 
spins or constructs a hibernaculum or a cocoon, in which to undergo its 
transformations, exemplifies the potent power of heredity in transmit- 
ting acquired peculiarities. A hundred species of parasitic larvee, e. 4., 
of the family Braconide, which in themselves are almost or quite indis- 
tinguishable from one another structurally, will nevertheless construct 
a hundred distinctive cocoons—differing in form, in texture, in color, 
and in marking—each characteristic of its own species and in many 
instances showing remarkable architectural peculiarities. These are 
purely mechanical structures, and can have little or nothing to do with 
the mere organization or form or structure of the larva, but they illus- 
trate in the most convincing manner the fact that the tendency to con- 
struct and the power to construct the cocoon after some definite plan 
must be fixed by heredity, since there is no other way of accounting 
for it. This fact alone, which no one seems to have thought of in the 
discussion, should be sufficient to confound the advocates of the non- 
transmissibility of acquired characteristics. 
Thus to my view modification has gone on in the past, as it is going 
on at the present time, primarily through heredity, in the insect world. 
I recognize the physical influence of environment; I recognize the effect 
of the interrelation of organisms; I recognize, even to a degree that 
few others do, the psychic influence, especially in higher organisms— 
the power of mind, will, effort, or the action of the individual as con- 
tradistinguished from the action of the environment; I recognize the 
influence of natural selection properly limited; but above all, as mak- 
ing effective and as fixing and accumulating the various modifications 
due to these or whatever other influences, I recognize the power of 
heredity, without which only the first of the influences mentioned 
can be permanently operative. 
Let us stop for a moment to ponder what the intricate adjustments 
between plants and animals, and especially between plants and insects, 
mean when they have become so profoundly modified by each other that 
their present existence actually depends the one on the other. As 
paleontology shows, and as Prof. Ward has more particularly so well 
explained, there was for ages no vegetation but the flowerless plants. 
The first were the low cellular cryptogams, consisting chiefly of ma- 
rine algve, and these, the lowest and first organisms upon the planet, 
have endured through all geologic time and obtain to-day. Next, be- 
ginning in the upper Silurian, and reaching their maximum in the Car- 
boniferous, came the vascular cryptogams, of which the ferns con- 
Stituted the bulk. Arborescent and gigantic, as ‘compared with pres. 
ent forms, they mingled with the now extinct Lycopodinee to form the 
bulk of the forests of the coal period. Then came the Phznogams, or 
flowering plants, and in this great division the Cycadacee and Coni- 
