Appendix. 541 



"The pupa of this last species has nothing peculiar in its 

 general appearance, but possesses the ordinary pupal 

 form ; it is tolerably rounded, without any great eleva- 

 tions or depressions ; a minute pointed projection is 

 situated on the head over each eye-cover, and a similar 

 process projects from the roots of the wings. Its dis- 

 tinguishing characters are five pairs of spines on the 

 back of the abdominal segments. These spines are found 

 also in Acrtea Alalia, but appear to be absent in other 

 species, e.g. in the Indian A. Viola. Last summer, 

 among some batches of Thalia larvae each batch being 

 the progeny from one lot of eggs I found certain indi- 

 viduals which differed from the others in having much 

 shorter spines, and these changed into pupas in which 

 the five pairs of spines were proportionally shorter than 

 usual, thus being an exception to the rule that changes 

 in one stage of development are without influence on 

 the other stages. I may remark, by the way, that this law, 

 enunciated by Weismann, can only be applied to imagines 

 and pupa; with certain restrictions. The skin of the pupa 

 forms a sheath or cover for the eyes, antenna?, trunk, 

 legs, and wings of the imago, and if these parts undergo 

 any considerable modification in the latter, corresponding 

 changes must appear in the pupa. This is shown, for 

 instance, by many ' Skippers ' (Hesperidte\ t in which the 

 extraordinarily long trunk necessitates a sheath of a 

 corresponding length. The colour of the pupa of Acraa 

 Tlialia is whitish, the wing-veins with some other 

 markings and the spines are black ; metallic spots are 

 absent 



" In the pupa of Heliconius Eucra/tthe laterally com- 

 pressed region of the wings is raised into a large pro- 

 jection, the antennal sheaths lying on the edges of the 

 wings arc serrated and beset with short pointed spines ; 

 instead of the minute projections of Acrtra Tlialia, the 

 head bears two large humped processes ; the body is 



