406 Specific Identity of the 
calm sunny day, another naturalist observed a prodigious 
flight of the common cabbage butterflies (Papilio brassice), 
passing from N. E. to S. W. for two hours. Another swarm 
of these insects was met with midway in the British Channel ; 
and I have myself observed some wanderers in the Atlee; 
at least seventy or eighty miles from land, flitting away appa- 
rently without fatigue, and not even settling to ret upon the 
rigging. Mr. Lindley, a writer in the Royal Military 
Chronicle, tells us that in Brazil, in the beginning of March, 
1803, for many days successively, there was an immense flight 
of hints and yellow butterflies, probably of the same fies as 
the cabbage butterflies. They were observed, like my friends 
in the Atlantic, never to settle; though, as ee course was in 
a direct line for the ocean, andl they x were last seen at no great 
distance from it, they probably ultimately became victims to 
the innate feeling which prompted them to quit the land. 
With these instances on record, we may conclude that, if 
such things take place at noon-day amongst the diurnal lepi- 
dopterous S insects, under the shades of night the crepuscularian 
tribes of Lepidoptera, impelled by a similar unaccountable 
instinct, may wing their way over tracts of country, unsus- 
pected and unobserved, till some accident like the before- 
mentioned may arrest their career, and present them to the 
wondering eyes of naturalists, mG: but from some such theory 
as migration, can account for mysterious appearances of these 
minor tenants of the air, whose visitations are so few and far 
between. 
June 28. 1830. E. S. 
Art. V. On the Specific Identity of the Primrose, Oxlip, Cows- 
lip, and Polyanthus. By the Rev. Joun Stevens HENsLow, 
Professor of Botany in the University of Cambridge. 
Sir, 
Our knowledge of vegetable physiology has not been 
hitherto sufficiently advanced, to furnish us with any precise 
rule for distinguishing the exact limits between which any 
given species of plant may vary. Hence the most accurate 
observers often differ in their opinions, whether two or more 
individuals should be considered as mere varieties of the same, 
or be raised to the rank of separate species. Indeed, the 
more accurate our powers of discrimination become, the more 
inclined we seem to be to multiply species. There are, how- 
ever, certain stubborn, well-authenticated facts, which tend to 
lower the authority of that discriminating tact which the ac- 
