n 



because they are still quite unknown or for other reasons, I shall have to 

 give a great many plates in quarto which, though the figures have been 

 made already, will amount to a pretty large sum of money and there are 

 still the printing-and publishing costs of the text, and the inevitable translation- 

 fees. And who can guarantee that the produce of such a work will even 

 slightly lessen the expenses? 



Therefore I have resolved to try it by publishing the said fauna of the 

 Rhopalocera in separate monographies according to families instead of the 

 whole work at once. To the first monography, which will serve at the same 

 time as a proof, I intend to add, according to the amount of financial support 

 given in this way to the publication, a subscription list for the next, in 

 order to be able to judge of the possibility of continuing it. As the first family 

 to be treated of in this way, I have chosen that of the Pieridje. This one 

 seemed most suitable to my purpose. Firstly, because it is not very numerous 

 in species living in Java, while at the same time there already exist good figures 

 of many of them, so that a relatively small number of plates will suffice. 

 Secondly because the said family especially offers the occasion to speak about 

 some lepidopterological views which I profess, contradictory to the prevailing 

 opinions in this respect, and thus enables me to explain these views in examples, 

 from the beginning. For this reason my work has a peculiar character, especially 

 with respect to the evolutionary nature of the morphogeny of the Lepidoptera. 

 Therefore, to my mind, in that regard it is also scientifically further advanced 

 than previous works which treat of the lepidopterological fauna of any other 

 region. In order to be able to judge correctly of my work, it is, however, 

 necessary to understand my said scientific views clearly from the beginning. 

 These views concern : 

 I. My absolute rejection of the minicry theory and of all that is connected 



with it. 

 II. The importance of the fact, hitherto biologically neglected, of the pheno- 

 menon of evolutionary atrophy to which the Lepidoptera are subject. 



III. The revelation of this fact by the phenomenon which I have called that 

 of the colour-evolution. 



IV. My appreciation of the differences of colour among tropical butterflies, 

 founded on this phenomenon, which are generally thought to be forms 

 of the dry and of the rainy season. 



V. The process of the phenomenon, referred to under II, in the gradual 

 disappearance of the hind-wings. 

 I have already published several essays on these subjects. The principal 

 are the following : 



