OF AUTS AxND SCIENCES. 235 



exclude entirely a third factor, sexual selection. Everybody will fol- 

 low Professor Weismaun's careful and elaborate study with interest, 

 though it is probable that the examination of a larger number of 

 exotic species (he has chiefly used European) will change, or at least 

 modify, some of his statements.* 



Nevertheless, if it if to be assumed with Professor Weismann that 

 the colors and the pattern originate in a purely mechanical manner, 

 there seems to be a large gap still to be filled. The statement that 

 color and pattern appear in a caterpillar by selection and adapta- 

 tion as a beneficial protection, without showing how they have been 

 produced, where they come from, which part of the body, and what 

 kind of chemical process brings them out, represents simply a belief. 

 Belief is, as it is well known, beyond discussion, as long as it is based 

 upon views which cannot otherwise be proved. But as the author 

 has prominently advanced that the origin of the color and the pat- 

 tern is only the consequence of mechanical arrangeraents, excluding 

 entirely predetermining power, the possibility of such mechanical 

 arrangements should have been proved satisfactorily. 



If we compare side by side Sir Charles Lyell's letter with the 

 accepted predetermination and Professor AYeismann's work with the 

 denied predetermination, there seems to be no difference except in 

 the belief of both authors. 



The conviction that color and pattern are the consequence of exist- 

 ing laws and actions in the body of the insect, induced the present 

 writer to extend his study in that direction. May it not be considered 

 too assuming, if the result shall prove inadequate to the purpose. The 

 first step in all such questions is the most difficult, and often noth- 

 ing moi'e is left to be said about it, except that it was the attempt 

 of the first step.f 



* Of North American Sphingidse the previous stages of fifty-four species 

 are known, and of fifteen species all stages. "With very few exceptions all 

 were published before 1874. Of the European species all stages were de- 

 scribed long ago of eight species : Sphinx ligustri by Schwarz ; Sph. pinastri 

 by Sepp, Ratzeburg, Hartig, Schwarz, Klopsch ; Deil. euphorhkz by Sepp, Rosel, 

 Schwarz ; Deil. porcelliis by Sepp; Smer. tilice by Rosel, Reaumur; Smer. ocellata 

 by Sepp ; Smer. popitli by Sepp, Schwarz ; Deil. nerii by Rossi. With few ex- 

 ceptions excellent figures are given. The literature is tlierefore not so scanty 

 as has been assumed, though not sufficient for the purposes of the author. 



t Some parts of the present paper were publislied in the Amer. Natural. 

 1872, pp. 388-;3r)3, and Entom. Monthly Mag. 1872, ix. pp. 78-83, Mimicry in 

 the Colors of Insecta. 



