Rev. F. D. Morice's Notes o>i Australian Sawflies. 305 



different centres of distribution by similar routes, helped 

 or hindered from time to time by similar causes. For 

 whatever physical barriers — such as seas, rivers, mountains 

 running east and west, deserts, intolerable climates and 

 temperatures, absence of certain kinds of vegetation, 

 etc., etc. — would present unsurmountable obstacles to 

 the migrations of a rather feeble and sluggish herbivorous 

 Mammal, would also restrict the distributions of most 

 genera of Sawflies; and, on the contrary, in both cases 

 such circumstances as sudden complete and long-continued 

 isolation in a favourable district through the disappearance 

 of land-bridges by which they had entered it would tend 

 to the rapid multiplication and differentiation into new 

 forms of some few stocks in that particular district, while 

 everywhere else they might be extinguished by the com- 

 petition with them of their superiors. Thus it is, perhaps, 

 not to be wondered at that Australia should have a Fauna 

 consisting, alike as to its Mammals and its Sawflies, of 

 genera and species apparently well-differentiated and fairly 

 flourishing, but representing a very small and probably not 

 the most characteristic part of — not the present Oriental 

 Fauna, but the Fauna which occupied that Region before 

 Notogaea ceased to be in contact with it ! 



Nor, when we reflect on the long ages that have elapsed 

 since that contact finally ceased, and the multitude of forms 

 that must have since been developed or become extinct 

 on both sides of Wallace's Line, will it surprise us that the 

 present Australian Sawflies should no more resemble those 

 of the Oriental Region than those of any other part of the 

 world, or that the forms most resembling them should 

 happen to survive only in a country so distant as Neogaea. 

 Nearly the same has been the case with the Mammals. 

 And we may, perhaps, regard the phenomenon as some- 

 what parallel, though on a much larger scale, to that of a 

 country peopled throughout almost its whole extent by 

 certain dominant races, but with a few dwindling remnants 

 of tribes which had failed to hold their own in the interior 

 lingering on still, at points very far apart, in adjacent 

 islands, or headlands on its coasts.. Alike in Australia and 

 in South America the southward migrations of Sawflies 

 appear to have reached their extreme limits; * the vegeta 



* I have sought in vain for any record of Sawflies from Patagonia 

 or South Chili. Darwin's collections made there and now in B.M. 

 include_not one of that group ! 



