1883-84] Edinburgh Naturalists Fie/d C/iib. 169 



having considerable elevations, and we think that the evidence 

 obtained from those countries only helps to bear out the belief Ave 

 have, that the further Avest we go Ave find the flora more restricted. 

 If Ave compare Scandinavia Avith Iceland, Ave find the same rule 

 again applies, for Decandolle gives 402 as the number of varieties in 

 that island, Avhich is of large extent, having great elevations, and a 

 less rigorous climate than Norway and SAveden, — yet the decrease is 

 very great. If Ave compare England Avith Ireland, there is the same 

 falling off in the number of varieties the further west we go ; and if 

 Ave do the same Avith the mainland of Scotland, and Colonsay and 

 Oronsay, it is only to obtain an illustration of the same fact, as there 

 is not a single plant found on Colonsay and Oronsay that is not also 

 found on the mainland. Take these islands, and compare them Avith 

 Ireland, remembering the limited area coA^ered by the former com- 

 pared with the latter, and we Avill find, after making all alloAvance 

 for those differences, and the presence of higher elcA^ations in Ireland, 

 that probably the two floras represent forms of plant life in nearly 

 the same ratio of abundance. These statistics and remarks do not 

 refer to Mosses, or any of the loAver forms of vegetation. 



The fauna is more difficult to obtain information about, but Ave 

 have the evidence acquired by the excavations in our English bone- 

 caves, especially Kent's Cavern, which all point to two periods Avhen 

 different migrations of animals into Britain took place. It is generally 

 supposed that the neAver forms, Avhich are consj^icuous by the absence 

 of their remains in the loAver strata of the caves, but Avhich become 

 common in the upper strata, must have come to Britain overland by 

 a recent connection with the Continent. Those English caves have 

 yielded abundant remains of animals, principally mammalia, but Ave 

 merely mention the fact in passing, as Ave intend only to refer to the 

 reptilian fauna, and, as regards that, very briefly. In his interesting 

 and instructive book, ' Island Life,' Mr Wallace gives the folloAving 

 information regarding the distribution of reptilia and amphibia, Avhich 

 shows the remarkable diminution in the number of varieties the 

 further west Ave proceed ; and the same fact is said to be observarble 

 as regards the mammalia, from a study of their past and present 

 distribution : — 



Belfjium, . . .22 species of reptilia and amphibia. 



Crmat Britain, . . 13 ,, ,, ,, 



Ireland, . . . 4 ,, ,, ,, 



The decrease from 22 to 13 and from 13 to 4 species is very great; 

 but that it is not singular may be understood from our OAvn observa- 

 tions on Colonsay and Oronsay, for there Ave find only tAvo varieties 

 of reptilia — namely, the SloAv-Avorm {Angiiis fragilis) and the Green 

 Lizard (Zootoca vivipara), and no amphibia. It is possible that the 

 absence of Snakes, and such common forms of amphibia as the Toad 



