877 



and actions, and they pcrlonu acts which, however vohiutary, and, as I 

 believe, conscious, in many cases, as in that of our Yucca moth, could 

 not be performed were the tendency n()t iidieiited. Every larva which 

 spins or constructs a hibernaculuni or a cocoon, in which to undergo its 

 transformations, exemplifies the i)otent power of heredity in transmit 

 tiuj? acquired peculiarities. A liuiidred si)ecies of ])arasiti(; larva', <■. r/., 

 of the family Braconiihe, which in tln'iiisclves are almost or quite indis- 

 tinguishable from one another structurally, will nevertheless construct 

 a hundred distiuctive cocoons — differing in form, in texture, in color, 

 and in markingveach 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 vStructure 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. 



Tlius 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 properlj^ limited; but above all, as mak- 

 ing effective and as fixing and accumulating the various modifications 

 due to these or whatever other influences, I rec^ognize 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 profinmdly 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 alga?, and these, the lowest and first organisms upon the planet, 

 liave 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 <'ryptogams, of which the ferns con- 

 stituted the bulk. Arborescent and gigantic, as compared with pres 

 ent forms, they nnngled with tlie now extinct Lycoi)odine{e to form the 

 bulk of the forests of the coal i)eriod. Then came the Phccnogams, or 

 flowering plants, and in this great division the Cycadacea* and Coni- 



