Ixxxii MEMOIR. 
until the high Andes had been explored at elevations near the 
snow line. This Mr. Whymper has done so thoroughly that, “if 
there had been any distinct element of a north temperate or 
south temperate coleopterous fauna on the Ecuadorian Andes, the 
collections he made, inexhaustive though they may be, would have 
shown some traces of it; but there are none.”* Bates, therefore, 
answers the question in the negative. “It seems to me a fair 
deduction from the facts that no distinct traces of a migration | 
during the lifetime of existing species, from north to south, or véce 
versa, along the Andes, have as yet been discovered, or are now 
likely to be discovered. It does not follow, however, that the 
Darwinian explanation of the peculiar distribution of species and 
genera on mountains in the tropical and temperate zones, and in 
high latitudes of the Old World, is an erroneous one. The 
different state of things in the New World is probably due to the 
existence of some obstacle to free migration, as far as regards 
insects, bétween north and south, both during and since the glacial 
epoch.” | Such an obstacle might exist in “a breach of continuity 
of the land in glacial times at the Isthmus of Panama,” or in 
the lower altitude of the.tropical Andes during that epoch, which, 
while favouring “the spread of tropical forms over the whole area, 
would successfully resist the invasion of high northern or southern 
species.” 
This reference to Bates’s latest contribution to the problem of 
geographical distribution, further goes to show how unslackened was 
his grasp of the philosophical side of any question that he handled. 
In an age of excessive specialisation of every department of science, 
when, like the builders of the Tower of Babel, a man knows not 
the language of his fellow-worker, Bates will have a larger place, 
not so much for his classification of materials, as for his insight 
into their significance. In his second presidential address to the 
Entomological Society of London, delivered January 15th, 1879, 
he speaks of a deceased member of the Society as follows :— 
‘‘In judging of his position as an entomologist, we must consider him 
chiefly as an zconographer ; but in this useful sphere he was faczle princeps. 
I am not aware that he advanced any views as to classification, and he rarely 
even described new genera. The structural characters of the fascinating 
objects of his study he for the most part ignored; and it was amusing, to those 
who knew him, to observe how persistently he declined to accept the great 
aid to classification and estimate of natural affinities afforded by the form of 
gf IGE Mon ee Tt Licey P+ 5- 
