38 
MEMOIES OF THE NATIOJTAL ACADEMY OF SCIENCES. 
ancestral forms into the ])resent series of genera, subfamilies, and families represented such a 
great number of species ? 
Indeed, it seems difficult to account for the evolution of the vast hordes of existing species of 
insects, unless we assume that there was going on throughout the entire process the rise and 
gradual ])erfecting of postnatal acquired characters, such characters becoming fixed by heredity 
and reappearing witlt unerring certitude at different stages in the life of the individual, while in 
some animals whose postnatal metamorphosis became suppressed we have the more salient stages 
eintoniized during the life of the embryo. 
The reddish and russet spots developed in the three, and especially two, last stages of the larva 
of these IN'otodontians are, as shown by the experiments of Wood, and especially of Poulton, the 
result of the environment, being due to the action of the color of the S])ots of the leaves on the 
sensitive portions of the skin or cuticle of the cateri)illars. It seems to be fundamentally due to 
the action of both x>hysical and physiological processes. The skin is spotted and x)ainted by the 
reflection of the red and russet tints of the leaves on the sensitive skin of the living organism. 
The results are inherited at a coiTes])onding period of life, just as the tubercles, spines, horns, 
and other kinds of armature. Hence for thousands of generations we liave had such spotted 
caterpillars. Kow if, as is quite obvious, the spots are thus suddenly ]>rodiiced, since light and 
dark hues were so produced in Mr. Poulton’s laboratory, at a certain time in the life of the cater- 
jiillars observed by him, as we know by his ex])eriments the colors were produced in the individuals 
of a single generation, it woiild seem to follow that in nature the characters were thus acquired in 
the larva at a certain stage in the life of the individual, and have been transmitted by homochronous 
inheritance. Moreover, this appears to be a case Avhere the characters have been produced by 
the direct action of the environment. 
At the time, the last of summer, when the leaves are fully mature, preparing to fall off and 
beginning to be variously simtted and tinted, tliere is made ready the peculiar environment of these 
leaf-feeding larvm, and so long as these conditions of red and russet spotted or tinted leaves exist 
we shall continue to have similarly spotted caterpillars; should the leaves remain green, we should 
not expect to have such spotted larvie. [Mow, these changes in the larvic are due to the ijrimary 
factors of organic evolution, i. e., to changes in the environment, to the reflection of these bright 
or russet colored patches on the cuticle of the animal. By the neo-Darwinian, the organization 
and xnoductiou is attributed to “natural selection,” as if it were the main and only efficient cause 
of evolution, but really it is not so at all. It may act as a subordinate factor after the colors are 
X^roduced, and serve to preserve those individuals most distinctly marked, those less so more 
readily falling a prey to birds and insects. A^atural selection does not originate, but after the new 
structures or markings have appeared, as the result of the operation of the primary factors of 
organic evolution (the views of neo-Lamai'ckians), natural selection comes in as a late and quite 
subordinate factor to x^reserve the organism. 
Family Ceratocampklw , — It is easy to believe that this group might have evolved from such a 
thoroughly armed caterpillar as tliat of Heterocampa guttiviitaj whose ontogeny we have just out- 
liued, as all the Ceratocampidm bear spines which vary in degree of complexity. We are now 
acquainted with the life history of each importaiit genus of this interesting group. We will select 
the caseof Z/ic(>7or, a creature of marvellous beauty of ornanieutatiou, which feeds 
on the Gleditschia or spiny locust. After a detailed study of the larva through its first larval 
stages to its maturity, we have drawn up the following summary of the more salient features in 
its ontogeny, dividing the characters into those which are congenital and those which Ave believe 
to have been acquired diu’ing the stages succeeding the first: 
STTMMARY OF THE SALIENT FEATURES IN THE ONTOGENY OF SPIIINGICAMPA BICOLOR. 
A. COXGEXITAI. CHARACTERS OF THE LARVA, ALL APPKARIXG IN STAGE I. 
1, The two imirs of enormous sx^iues of second and third thoracic segments one-half as long 
as the body and ending in a two-spined, large, flattened, dark bulb, freely movable and plainly 
defensive in function. 
2. The large, reddish, spiny ‘^caudal horn” on the eighth uromere ending in two bristles. 
