Packard.] 
560 
[Feb. 1£» 
which is humped on the eighth abdominal segment, connects with 
the plain-bodied L. carmelita and the above mentioned group, Phe- 
osia, Leiocampa) should properly by their smooth, noctuiform 
shape stand at the bottom of the family, as being nearest related to 
the primitive form of the group. But until we know more of the 
earliest stages, it is best to suspend our judgment. 
1. The more prominent tubercles, and spines or bristles arising 
from them, are hypertrophied piliferous warts, the warts with the 
seta or hair which they bear being common to all caterpillars. 
2. The hypertrophy or enlargement was probably primarily due 
to a change of station from herbs to trees, involving better air, a 
more equable temperature, perhaps a different and better food. 
3. The enlarged and specialized tubercles developed more rap- 
idly on certain segments than others, especially the more promi- 
nent segments, because the nutritive fluids would tend to more 
freely supply parts most exposed to external stimuli. 
4. The stimuli were in great part due to the visits of insects and 
birds, resulting in a mimiciy of the spines and projections on the 
trees ; the colors (lines and spots) were due to light or shade ; with 
the general result of protective mimicry, or adaptation to tree-life. 
5. As the result of some unknown faeior some of the hypodermic 
cells at the base of the spines became in certain forms specialized 
so as to secrete a poisonous fluid. 
6. After such primitive forms, members of different families, had 
become established on trees, a process of arboreal segregation or 
isolation would set in, and intercrossing with low-feeders would 
cease. 
7. Heredity, or the unknown factors of which heredity is the re- 
sult, would go on uninterruptedly ; the result being a succession of 
generations perfectly adapted to arboreal life. 
8. Finally the conservative agency of natural selection would 
operate, constantly tending towards the preservation of the new va- 
rieties, species and genera, and would not cease to. act, in a given 
direction, so long as the environment remained the same. 
9. Thus in order to account for the origin of a species, genus, 
family, order, or even a class, the first steps, causing the origination 
of variations, were in the beginning due to the primary (direct 
and indirect) factors of evolution (Neolamarckism), and the final 
stages were due to the secondary factors, segregation and natural 
selection (Darwinism). 
