412 JOURNAL OF SCIENCE. 
nent during greater part of the tertiaryera. But the distribution 
of the lower animals, together with the absence of palzeozoic and 
mesozoic rocks on oceanic islands, tends to prove that in pre- 
tertiary times the distribution of land and sea was very different 
to what it isnow. The geological evidence is unsatisfactory, as 
it is all negative. There is no positive evidence that the deep 
sea has ever been land. There is no positive evidence that any 
continental area has ever been deep ocean ; and there is no posi- 
tive evidence that any one of them has alwaysbeen land. There 
is positive evidence that most of the continental areas have often 
been land since the Cambrian period, but the positive evidence 
is not continuous ; there are long periods of unrepresented time ; 
and, as Mr. Darwin says, “we do not know what was the state 
of things in the intervals between the several successive forma- 
tions; whether Europe and the United States during these in- 
tervals existed as dry land, or as a submarine surface near land, 
on which sediment was not deposited, or as the bed of an open 
and unfathomable sea.” 
— ae 
SOME EFFECTS OF THE RABBIT PEST. 
cree tee eee 
BY D. PETRIE, M.A. 
Kitked &: ra 
It is some three or four years since the rabbit pest has reached 
a crisis in the interior of Otago. Their invasion and occupation 
of the country have been fruitful in serious results to squatters 
and their flocks. They have called into existence a new voca- 
tion, that of the rabbiter, who with his canine following is now a 
well-known figure in most parts of the interior. It is not, how- 
ever, the aim of this paper to descant on the effects of the rabbits 
on labour and settlement, but to point out certain other import- 
ant though less notorious results flowing from their encroachment 
and predominance. I refer to changes in the vegetation of the 
country that are being slowly but surély brought about by their 
agency. Some of these it will be seen are unexpected enough. 
First we may notice how they lead to the spread of thistles. 
This may be conspicuously seen in the Moa Flat and Ettrick 
districts, where thistles are gaining a firm footing high up on the 
hill sides, on what was a few years ago well-grassed pasture 
country. The rabbits and sheep together have for a series of 
seasons kept the grass down so thoroughly that an increasing 
area became year by year almost bare. On these bare spots the 
thistle seeds, wafted about by the winds, gained a ready footing, 
and as the grass has been and is kept very bare, they are spread- 
ing further and further. In the original condition of the land 
thistles throve only by road-sides, and on land disturbed and left © 
bare Dy floods and digging operations. Now, however, the 
general bareness of the soil is such that there is every prospect 
of thistles spreading very extensively over what used to be ex- 
