GUPPY ON PACIFIC CONTINENT 
325 
that the story of plant distribution in the Pacific is bound 
up with the successive stages of decreasing activity in the 
dispersing agencies. He thinks that the area of active dis¬ 
persion, as illustrated by the non-endemic genera of plants, 
at first comprised the whole of the tropical Pacific.* After¬ 
wards it was limited to the southern Pacific, and finally to the 
western Pacific only. The birds that carried seeds all over this 
ocean became more and more restricted in their range, pro¬ 
bably, as Mr. Guppy suggests, on account of increasing 
diversity of climatic conditions. The plants of necessity re¬ 
sponded to the ever narrowing conditions of bird-life in this 
ocean, the differentiation of the plant and bird taking place 
together. 
Mr. Guppy dislikes the idea of hypothetical alterations in 
the present relations of land and water, and yet what an 
amount of hypothesis he has to resort to in his endeavour to 
explain the theory which he is so anxious to support! There 
is not a scrap of evidence for the belief that dispersing 
agencies have practically ceased at the present time, nor that 
the migrations of birds have diminished. On the contrary, 
ornithologists have done their utmost to trace the origin of 
all bird migrations to the gradually increasing diversity of 
climatic conditions during the Tertiary Era, which they sup¬ 
pose to have culminated in the Glacial Epoch. Although we 
have little evidence for such a belief, it seems a reasonable 
supposition. But what can be said in favour of Mr. Guppy’s 
theory, that, owing to the increasing diversity of climatic con¬ 
ditions, the seed-carrying birds have become more restricted, 
that is to say, less migratory ? 
A careful perusal of Mr. Guppy’s work must make it evident 
to anyone, that, although plants have far greater facilities for 
accidental transport, and have in many cases actually been 
thus conveyed from one land surface to another, they agree 
on the whole perfectly with animals, in so far as the Pacific 
islands are largely tenanted by very ancient types. If we adopt 
the theory of accidental dispersal for the origin of the Pacific 
island flora, we must apparently assume that the means of 
occasional conveyance were far more efficient in former times 
* Guppy, H. B., “A Naturalist in the Pacific,” II., pp. 519—520. 
