POSTSCRIPT. 535 



print, some change might have been made in the second 

 chapter or division of this volume, where remarks occur 

 on the inequality and the permanence of species. — If 

 the ' Handbook of the British Flora ' by Bentham had 

 been sooner seen, probably it would have given en- 

 couragement to the rejection of several segregate species, 

 which are admitted into the lists printed on preceding 

 pages. Although it is thought that some among Mr. 

 Bentham's aggregations would not have been recom- 

 mended by botanists who devote a closer or more ex- 

 clusive attention to the plants of this country. 



While writing about the * areas of species ' or about 

 their arrangement under ' types of distribution,' a re- 

 ference might have been properly made to an article in 

 a late no. of the Zoologist, which was read with much 

 satisfaction by the writer of the Cybele. Messieurs 

 T. Boyd and A. G. More have there traced out the dis- 

 tribution of the Butterflies through the same eighteen 

 provinces ; and they have also tried how far the same 

 types of distribution might be found applicable to those 

 locomotive insects. Whatever the origin of the various 

 species of butterflies, natives of the British Isles, their 

 capabilities of self- distribution are so great, that it seems 

 reasonable to suppose their present distribution chiefly 

 determined by food and climate. The same writers 

 suggest that the land mollusks and other stationary 

 members of the fauna might be advantageously studied 

 on the same method. See Zoologist, no. 189, pages 

 6018 to 6027. 



On pages 55-6 a few words are borrowed from Lyell's 

 Principles of Geology. Possibly they may mislead when 

 there read apart from that Author's own text. Lyell's 

 doctrine is. Creation, at a very slow rate, relatively to the 

 total number of existing species. A special measure of 



