duced by natural selection, but that it did not necessarily 

 mean that darkening was the result of the same causes in 

 every locality. The dark varieties taken in Shetland and the 

 Hebrides were no doubt produced by a different preponde- 

 rating cause from that which resulted in the counties of York 

 and Lancaster. He spoke of the remarkable extension of 

 melanism in the two latter districts during the past fifty years, 

 making especial mention of TepJirosia biundiilaria, Bork., of 

 which now it was difficult to find a typical specimen, while 

 then it was equally difficult to get a dark variety. He con- 

 sidered that the use of coal, which had increased so enor- 

 mously in those districts of late, was the primary cause. The 

 vegetation was always dirty, and trees were permanently 

 blackened by the smoky deposit, thus rendering it necessary 

 for their own preservation that certain insects should assume 

 a garb assimilating more to their environment. Among other 

 species, he mentioned the increasing frequency of dark vars. 

 oi Ainphidasys betnlaria, L., Polia chi, L., and Aplecta nebii- 

 losa, Hufn. In some localities the type forms of these were 

 certainly rare. Several members had noted the increasing 

 numbers in which Hybernia leiicophaatia, Schiff., of a black, 

 suffused coloration, were taken, and Mr. Step said that, 

 around London for many miles, lichens had ceased to grow 

 on the sides of trees exposed to winds which carried an 

 appreciable amount of smoke. 



Mr. Adkin read the following communication from Mr. W. 

 Mansbridge : — 



" Many of you know that I spent last summer in the 

 Indian Territory of North America — a tract of land set 

 apart by the U.S. Government for the Indians, lying between 

 Kansas, north and Texas, south. 



" In driving across the prairie I was much interested in 

 watching the swallows hawk for the moths that were kicked 

 up by the horses. No matter how far we went, a flock 

 of swallows, varying in number from ten to fifty, some- 

 times nearer a hundred, always accompanied us. There 

 is usually a breeze blowing on the prairie, and of course 

 the moths went with the wind ; the swallows had found 

 this out, and accordingly always kept to windward of the 

 buggy, never crossing unless the impetus of a swoop carried 

 them over. 



" The quickness of eye of these swallows is wonderful ; 

 they seldom miss, and when they do the insect is never fol- 

 lowed, but is snapped up by some other bird. 



"The swallow is very like our English species, the only 



