xiv DISTRIBUTION 585 



where, arid several species of Galaxias, an exclusively Australasian, 

 South African, and South American Physostome The differences 

 between the marine Fishes, though obvious enough, are less funda- 

 mental, a fair proportion of the New Zealand shore-fishes belonging 

 to the same families, and in some cases even to the same genera 

 and species, as those of Britain. 



Among Mollusca the fresh-water Unio (fresh-water Mussel), are 

 found in both countries, but New Zealand has no species of the 

 common genus Helix (Land-snail), abundant in Great Britain, and 

 its molluscan fauna generally is very peculiar. 



The Insect-fauna of New Zealand is remarkable for the paucity 

 of Butterflies fifteen species against about seventy in Britain 

 and for the abundance of Moths, mostly belonging to the Micro- 

 lepidoptera and the Geometrina. The occurrence of Peripatus in 

 New Zealand furnishes another strong point of contrast. Amongst 

 fresh -water Crustacea the British Astacus is represented by an allied 

 genus Paranephrops. Among marine Crustacea many genera are 

 common to the two countries, but there are numerous peculiar 

 forms, and it is worthy of mention that the New Zealand species 

 of Palinurus belongs to a more generalized type than the British 

 species, having no stridulating organ. 



The British Earthworms all belong to the familiar Lumbritidce 

 (including Luvribricus) and Gryptodrilidce ; in New Zealand both 

 these families are absent, and the majority of the Earthworms 

 belong to the Acanthodrilidcu, including the genera Acanthodrilus, 

 Octochcetus, &c. Lastly, there are found in New Zealand at least 

 twenty species of Land Planarians and one terrestrial Nemer- 

 tean ; neither of these groups is represented in the land -fauna of 

 Britain. 



That these striking differences are quite independent of climate, 

 food, &c. ; in other words, that the environment in the one country 

 is in no way inimical to the fauna of the other, is shown by the 

 zoological history of New Zealand since its colonisation. Apart 

 from domestic animals, the Brown Rat (Mus decumanus) and the 

 House Mouse (Mus domesticus) are now as common in New 

 Zealand as in Britain ; the Babbit has become a plague, barely 

 kept in check by constant effort stimulated by severe legislative 

 enactments ; Deer flourish as well in the mountains of Otago as ill 

 those of Scotland; the Birds first noticed by a visitor to the 

 settled districts of the colony will probably be the Sparrow, Black- 

 bird, Thrush, Starling, and Goldfinch; and Trout have become 

 so thoroughly acclimatised in the streams and lakes, that in some 

 districts the poorer settlers, like the British apprentices of old, 

 decline to eat them. We thus learn to distinguish between the 

 native or indigenous fauna of a country, and the introduced fauna, 

 which owes its existence to human agency: in comparing the 



