("xxiv _.) 
Prof. E. B. Pourron exhibited a series of Precis octavia, 
(Cram.) var. natalensis Staud., and Precis sesamus, Trim.,, 
both captured and bred by Mr. G. A. K. Marshall at 
Salisbury, Mashunaland (5000 ft.) and read the following 
notes thereon :— 
“The specimens exhibited prove conclusively (as Mr. 
Marshall has shown in the July number of ‘The Annals and 
Magazine of Natural History,’ p. 30) that these two butter- 
flies, which differ so entirely in appearance and even in shape, 
size and habits, are seasonal forms of a single species. Mr. 
Marshall deserves the thanks of all naturalists for this dis- 
covery of the most wonderful example of seasonal dimorphism 
as yet known, and for the generous manner in which he has 
despatched to this country the invaluable material constitut- 
ing his evidence, so as to make it accessible for all time 
in the British Museum and Hope Collection. 
“ Entomology is deeply indebted to Mr. Marshall for his 
liberality now and at other times in placing large quantities 
of valuable material at the disposal of investigators, and for 
his readiness in undertaking biological observations ; and I 
desire specially to thank him for constant help, and for 
the valuable information contained in his letters, some of 
which I hope to lay before the Society. 
“The relationship between Precis octavia-natalensis and 
P. sesamus has been described by Mr. Trimen (8. Afr. Butt., 
i, and ili, app.), who connected the two forms by a number of 
comparatively rare intermediate varieties, which, having 
regard to the fact that the forms themselves had been captured 
in coitu, he regarded as probably hybrids. The conclusion 
that the two forms were examples of seasonal dimorphism 
was reached by Mr. C. N. Barker and independently by Mr. 
Marshall (Trans. Ent. Soc. Lond., 1896, p. 557). 
“Of this conclusion the specimens exhibited furnish 
absolute proof. They include in the first place specimens 
captured by Mr. Marshall towards the end of the wet (summer) 
and beginning of the dry (winter) seasons, 
The red form (natalensis) was captured on Feb. 13, 1898, 
(a pair in coitw) and Feb. 20, the blue form (sesamus), on 
March 2, 12 and 16, and April 2. The latter form was 
