41 



should be conceived as an extraordinary, inexplicable fact — a so-caled mutation — 

 instead of the result of a normal process of natural evolution. In that case 

 one is at a loss how to treat these numerous forms except to differentiate 

 them as numerous species or at least as races, which, however, are by no 

 ineans well defined but graduating into each other constitute but a confused 

 entity. It is only through grasping the principle referred to that it becomes 

 possible to understand these varied forms. It is true that in the case of a 

 species exhibiting such an amount of variation, like Cyllo Leda L., this is 

 by no means an easy task; I believe, nevertheless, to have succeeded in this. 



By a comparison of more than i 50 specimens from Java, aided by that of 

 about 70 from other regions I have convinced myself that the Cyllo butterflies, 

 occurring in Java, with the exception of a small number, forming a distinct 

 species — Cyllo Suyuuana Moore — all belong to the species Cyllo Leda L. 

 Neither do I attach any value to the subspecies, which Fruhstorfer recognizes. 

 With regard to the majority of species specially figured from British India by 

 Moore, I must also doubt their independent existence; considering, however, 

 that these do not occur in Java I have been unable to study them and, conse- 

 quently, I am unable to form a definite judgment in this respect. 



Two courses of evolutionary modification are to be observed with regard 

 to this species in Java. One being the decrease in size of the wings which I 

 have explained in my paper " lleber die sogenannien Schivdnze der Lepidopterc?i" . 

 {Deutsche Entomologisclie Zeitschnft Iris 1903), and to which I hope to refer 

 again when dealing with the Papilionidae. The continuous operation of this 

 process manifests itself here principally in the gradual disappearance of the 

 projecting points, the vestiges of a former greater expanse of the wings. In 

 many individuals of Cyllo Leda L. such appendages are still fairly evident 

 (pi. XV, fig. T,oo,p,g), but in others, especially in the fore-wings, they become 

 considerably smaller. Entomologists, who are insufficiently acquainted with this 

 evolutionary process, are constrained to base distinct species on these different 

 forms of wing; in this manner Elymnias Caudata Butl., for instance, although 

 nothing but an old form of E. Undularis Drury, is looked upon as a separate 

 species. These appendages, however, are nothing but such wing vestiges which 

 in many Papilios have remained in the form of the so-called tails, sometimes 

 even — as in the Achates form of Papilio Memnon L. — only in an old 

 9 form ; an instance which clearly proves that of specific difference there can 

 be no question here. Thus these appendages are still strongly in evidence in 

 9 specimens of Cyllo Leda L. having made little evolutional progress in this 

 respect and still exhibiting, therefore, an old form, which, moreover, like the 

 old Achates form of Paitlio Memnon L., have also sometimes remained 



