394 LAMARCK, HIS LIFE AND WORK 
“The Lamarckian factors (1) change (both direct 
and indirect) in the szlzeu, (2) need, and (3) habit, 
and the now generally adopted principle that a 
change of function induces change in organs,* and 
in some or many cases actually induces the hyper- 
trophy and specialization of what otherwise would 
be indifferent parts or organs;—these factors are all- 
important in the evolution of the colors, ornaments, 
and outgrowths from the cuticle of caterpillars.”’ 
Our present views as to the relations between the 
Lamarckian factors and the Darwinian one of nat- 
ural selection are shown by the following summary 
at the end of this essay. 
““ 1. The more prominent tubercles, and spines or 
bristles arising from them, are hypertrophied pilifer- 
ous warts, the warts, with the seta or hair which 
they bear, being common to all caterpillars. 
‘‘2, The hypertrophy or enlargement was prob- 
ably [we should rather say foss7bly] 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 devel- 
oped more rapidly on certain segments than on others, 
especially the more prominent segments, because 
the nutritive fluids would tend more freely to 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 mimicry of 
the spines and projections on the trees; the colors 
*E. J. Marey: ‘‘Le Transformisme et la Physiologie Expéri- 
mentale, Cours du Collége de France,” Revue Sctenti figue, 2° série, 
iv., p. 818. (Function makes the organ, especially in the osseous and 
muscular systems.) See also A. Dohrn: Der Urspruny der Wiedbel- 
thiere und das Princip des Functionswechsels, Leipzig, 1875. See 
also Lamarck’s opinion, p. 295. 
