160 Browne: The Aquatic Coleoptera of the Isle of. Man. 
no suggestion of such a post glacial land-connection, but says = 
‘ The case of the Isle of Man . . . can be met, I think, by the 
supposition that it was connected with Cumberland until quite 
recently, and quite independently of any connection between 
England and Ireland ; that the Isle of Man, in fact, was always. 
a cape or peninsula of the mainland, and only recently became 
separated by local subsidences or by the action of the sed.’ 
Now there seems to be no doubt that the Isle of Man was 
completely ice-bound during the glacial period. Ice-scratchings 
are found at the tops of the highest mountains, and a great 
glacier drove down upon the high ground from the north, 
depositing quantities of boulder clay at the north end of the 
island, and forming what is now the low northern plain. The 
problem of how the island obtained its fauna and flora, there- 
fore, commences with the disappearance of the ice. 
Geologists differ widely as to whether there has been any 
post glacial land-connection between the island and England, 
and their conclusions are reviewed by Dr. Scharff in the’ work 
already referred to. Dr. Dwerryhouse, who has _ specially 
studied the glacial period, tells me that there is no geological 
evidence of such land-connection, though it is possible that a 
boulder-clay bridge may have existed. Judging, however, by 
the rate of denudation on land since the glacial period, it seems 
doubtful whether sufficient time has elapsed to allow of the 
removal of all traces of:such a bridge. 
Dr. Scharff argues very strongly as to the necessity for 
land-connections to account for insular faunas and floras, and 
allows almost no value to the endless means of dispersal pos- 
sessed by both animals and plants. Although there is in many 
cases undoubted evidence that the so-called ‘ continental’ 
islands have, in past ages, been joined to the neighbouring main 
lands, I venture to think that the evidence which Dr. Scharff 
adduces in support of his line of argument is beside the mark. 
He makes such points as the following": ‘The animals die 
shortly after their arrival on foreign soil” fc.y mp. 2.4) sri rate 
tempts to acclimatise the Eng!ish species [of hare] have been 
made in a number of places in Iveland, but many of them have 
been failures, and not one has been a signal success ’ []. c., p.. 29]. 
‘ The two species of snails, Helix pomatia and Cyclostoma elegans 
both of which occur in England . . . were turned out in several 
suitable localities in Ireland by Thompson, but failed to estab- 
lish themselves” [l.c., 4. 32]. He quotes many similar cases 
and his attitude towards the question is seen in the following 
sentence : ‘ When we once more carefully review the evidence 
as to the undoubted difficulty attendant on intentional intro- 
duction of animals by human agency, placed as they often are 
in most suitable localities, we must feel that accidental intro- 
duction cannot play an important role in the making of the 
fauna of any country ’ [l.c., p. 32]. 
Naturalist, 
