210 Mr. T. Vernon Wollaston on 
the more central archipelago) that it was the Canaries, 
and not Madeira, from which the Mediterranean branch 
took its rise. And if this be the case, it appears to me 
that a north-westerly prolongation, or fork, from Teneriffe 
(vic the Salvages) to Madeira, and thence continued to 
the Azores, would give all that we require (in conjunc- 
tion with its partial subsequent disruption) to render the 
phenomena, as now met with, intelligible. 
If we accept some such explanation as this, the acci- 
dental methods of conveyance across wide oceanic barriers 
(whether on the water or through the air) , whilst credited 
with an appreciable amount of possible results, would not 
be required ; for in that case the modes of progression, 
even amongst species which are by nature phlegmatic and 
stationary, become comparatively simple, being over a 
continuous land. Yet I cannot but think, where an un- 
broken tract has to be taken into account, that we can 
ill-afford to dispense with the agency of even the ordi- 
nary winds (which in this Atlantic region blow nearly 
uninterruptedly from the north-east) in promoting the 
gradual migration of the insect inhabitants ; for it must 
be remembered that a considerable number of the latter, 
however sedentary in their modes of life, and disinclined 
(ike the Tarphii) to wander from a single spot, undergo 
their transformations within the pithy stems of plants, 
and these latter when accidentally broken off, or rent by 
storms, would be conveyed at all events slight distances 
even by the common breezes, and would thus transport 
their inmates, whilst in the larva state, to places near at 
hand which the imago would never have colonized. I 
lay unusual stress upon this fact, because if the winds are 
to have any acknowledged influence in conveying living 
organisms across a broad expanse of sea, it 1s clear that 
they must (as rightly contended by Mr. Wallace) be of 
an altogether exceptional kind,—indeed, emphatically, 
*“storms and hurricanes,” phenomena which are not only 
somewhat rare in these particular latitudes, but which, 
when they arise, blow almost invariably from the south 
(thus implying a migration in an opposite direction from 
that which the:facts, as now observed, most plainly indi- 
cate); and moreover the sluggish, apterous types, which 
are the ones so largely represented in these Atlantic islands, 
possess (on the average) bodies which are comparatively 
unwieldy, and of all others the least suitable for atmos- 
