172 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



We have, firstly, a somewhat small group of species 

 occurring in regions of the north and north-west, elsewhere 

 inhabiting only mountains and elevated moorlands. This 

 group has been called the Arctic, the Glacial, or the Celtic 

 Fauna, all terms which, to some extent, beg the question 

 at issue. Perhaps the Celtic is the better term, if we can 

 eliminate the idea that the group is necessarily comparable 

 with the Celtic race, ethnologically considered. Its range 

 is principally in Scotland and western Ireland. Several 

 species occur there which do not occur in England, .but no 

 single species occurs in England which does not also occur 

 in Scotland or Ireland, or both. Next we have a group 

 which contains by far the greater proportion of our species. 

 They have been called the Siberian immigration ; whether 

 their ultimate starting point was Siberia or not, it is clear 

 that their proximate origin was the plain of Central 

 Europe, that they arrived here from the south-east and 

 east, and that during their dispersal throughout this 

 country some obstacle, though probably not entire separa- 

 tion, prevented complete access into Ireland. These are 

 species generally but by no means equally distributed over 

 Great Britain, not restricted to elevation, but often rigidly 

 so by other conditions of environment ; from a maximum 

 density in the south and east, they thin out northward 

 and westward, till many of their forms are rare in Scotland 

 and some altogether wanting in Ireland. 



The third group is perhaps more difficult to define, and 

 its members cannot always be disentangled from those of 

 the second group. We should comprise in it all those 

 species whose distribution is exclusively southern or south- 

 western, and is often marked by extreme discontinuity. 

 This is known as the Teutonic element in its eastern and 

 the Iberian in its western extension. The former, the 

 south coast of England, the latter, the south and south- 



