170 



THE YOUNG 



NATUEALIST. 



ing the changes in some cases and the 

 want of change in others. But that 

 insular character and the special inter- 

 est attaching to it are necessarily lost 

 if our natural productions are mixed 

 with those of the Channel Islands on 

 no other ground than that they have 

 belonged to the English crown for 800 

 years. In Morris's British Moths the 

 writer argues that because the Jersey 

 Tiger (C. Hera) occurs in Jersey, and 

 Jersey plants are included in the Lon- 

 don catalogue, therefore C. Hera should 

 be included in our lists of British 

 Moths. But he does not attempt to 

 show that the plants are properly in- 

 cluded. We do not know much of the 

 strata composing the Channel Islands, 

 but our friend, Mr. H. H. Walker, of 

 Liverpool, tells us "The largest, Jersey, 

 contains in part beds of slate and other 

 protozoic rock. This island, in fact, 

 is formed entirely of these rocks to- 

 gether with granite. This latter stone 

 is of true volcanic origin, including in 

 its composition crystals of quartz, 

 feldspar and mica. Guernsey consists 

 of equal proportions of granite and 

 gneiss. Here we have a volcanic in 

 juxtaposition with a metamorphosed 

 sedimentary rock. Sark, again, is 

 entirely granitic, while in Alderney we 

 have porphyry (another igneous granitic 

 rock) together with old red sand- 

 stone (?)" The nearest British land 

 is, we believe, the coast of Dorset or 

 Devon, but the nearest land to the 



I'rench coast, where probably the con- 

 nection of England with the continent 

 was last severed, is the chalk hills of 

 Kent. Chalk is a deep-water formation, 

 while the Channel Islands are shown 

 above to be of volcanic origin. It 

 seems quite possible then, that these 

 islands may have been formed since 

 Britain was separated from the conti- 

 nent ] but, at all events, their geologi- 

 cal structure is not similar to that of 

 the nearest part of Britain, nor yet of 

 that part nearest the continent ; and, as 

 a consequence, we would expect to find 

 plants growing there that do not occur 

 in those portions of Britain nearest to 

 them, and, in fact, several plants are 

 found there that do not grow in Britain 

 at all. Birds and insects can cross a 

 considerable extent of water, and it is 

 no wonder that French or Channel 

 Island species are occasionally taken 

 on our southern shores. That they 

 have so rarely established themselves 

 there is another evidence that they do 

 not belong to us, and other species have 

 never been taken here at all. The ques- 

 tion is not a very important one perhaps, 

 but the importance of insular species 

 being separately studied is becoming 

 better understood, and if collectors like 

 to admit Channel Island specimens to 

 their British collections they should 

 certainly so label them that it may be 

 understood where they were taken. 

 The desire to possess DapUdice, Latho- 

 niUf EuphorhicB, &c., no doubt makes 



