All these butterflies were very uniform in size, being about that of the ordinary _Telamonides_. The specimens of _Telamonides_ especially were “strongly marked, the crimson band in a large proportion of them being as conspicuous as is usual in _Walshii_, and the blue lunules near the tail were remarkably large and bright coloured. Of the _Marcellus_, in addition to the somewhat reduced size, the tails were almost invariably shorter than usual and narrower, and instead of the characteristic single crimson spot, nearly all had two spots, often large. In all these particulars they approach _Telamonides_.” Adding to the _Telamonides_ which emerged after August 20th most of those specimens which were found dead in the box at that date, the total number of this form is thus brought up to nearly 50. Of the 122 pupæ with which Mr. Edwards started, 28 remained in a state fit for hibernation, several having died without emerging. Previous experiments had shown that 28 out of 122 pupæ is not an unreasonable number to hibernate, so that the author concludes that the butterflies which emerged the same season would have done so naturally, and the effect of the artificial cold was not “to precipitate the emerging of any which would have slept” till the following spring. Now under ordinary circumstances all the butterflies which emerged the same season would have been of the _Marcellus_ form, so that the cold changed a large part of these into the form _Telamonides_, some (probably from those pupæ which experienced the lowest temperature) being completely changed, and others (from those pupæ which were only imperfectly subjected to the cold) being intermediate, _i.e._, only partly changed. It appears also that several pupæ experienced sufficient cold to retard their emergence and stunt their growth, but not enough to change their form, these being the 13 recorded specimens of _Marcellus_. Had the degree of cold been equal and constant, the reversion would probably have been more complete. The application of cold produced great confusion in the duration of the pupal period, the emergence, instead of taking place fourteen days after the withdrawal of the cold, as might have been expected from Dr. Weismann’s corresponding experiment with _Pieris Napi_ (Appendix I. Exps. 13 and 14), having been extended over more than two months. From the results of this experiment it must be concluded that _Telamonides_ is the primary form of the species. ADDITIONAL EXPERIMENTS WITH PAPILIO AJAX. [_Communicated by_ Mr. W. H. EDWARDS, _November 18th, 1879_.]