4306 Sj)eci/ic Identity of the 



calm sunny day, another naturalist observed a prodigious 

 flight of the common cabbage butterflies (Papilio brassicae), 

 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 Atlantic, 

 at least seventy or eighty miles from land, flitting away appa- 

 rently without fatigue, and not even settling to rest 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 imaiense flight 

 of white and yellow butterflies, jirobably of the same tribe as 

 the cabbage butterflies. They were observed, like my friends 

 in the Atlantic, never to settle; though, as their course was in 

 a direct line for the ocean, and they 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 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, who, 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. 18SG. E. S. 



\ 



Art. V. On the Specific Identity of the Primrose, Oxlip, Cows- 

 lip, and Polyanthus. By the Rev. John 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- 



