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APRIL 15, 1915| 
NATURE 
189 

of the Saleve. This mountain, which rises about 
3000 ft. above Geneva, consists of limestones and 
shales (Upper Jurassic and Neocomian), with Middle 
Tertiary sandstones, chiefly molasse, and glacial de- 
posits. Apart from the effects of altitude, the flora is 
much affected by the nature of the rock on which it 
grows, and besides this, a small colony of special 
plants generally accompanies any local physical pecu- 
larity. Of this association the large erratics of 
Alpine granite and schists afford a remarkable instance. 
Asplenium septentrionale is the only phanerogamous 
plant found on them to which rocks, in the High 
Alps, it is practically restricted. 

BLOOD-PARASITES AND FLEAS. 
Eos the past five years Prof. E. A. Minchin and Dr. 
J. D. Thomson have been engaged upon the inves- 
tigation of the rat trypanosome, Trypanosoma lewisi, 
with special reference to its relation to the rat flea, 
Ceratophyllus fasciatus. The results of this laborious 
and painstaking research are now published in the 
Quarterly Journal of Microscopical Science. They 
form a comprehensive monograph which occupies the 
whole of the last part of this journal (vol. Ix., 
part 4) and will undoubtedly be a standard work of 
reference for students of these very important blood- 
parasites. The fact that the authors have dissected 
and examined more than 1600 fleas in the course of 
their investigations shows the thoroughness with 
which the work has b2en carried out, while the artis- 
tic treatment and accuracy of detaii contributed by 
the illustrations, for which due acknowledgment is 
made to Miss Rhodes, leave nothing to be desired. 
T. lewist is fortunately a non-pathogenic parasite, at 
any rate so far as the rat is concerned, and it cannot 
live at all in human blood. It therefore forms a much 
more suitable type for general study than such deadly 
species as those which are conveyed by the tsetse-fly 
in Africa, and are responsible for fly-disease amongst 
horses and cattle, and for sleeping sickness in human 
beings. The authors give a very useful account of 
the technique employed in their investigations, and, 
incidentally, throw a good deal of light upon details 
of the anatomy and histology of the flea. 
The flea, of course, receives the parasite with the 
blood which it extracts from the rat, but apparently it 
cannot infect the rat by inoculating trypanosomes into 
it through the proboscis. The rat is supposed to 
become infected through the mouth; in the process of 
licking its fur it takes in trypanosomes with faecal 
matter deposited by the flea; or it may become infected 
by eating infected fleas. 
While in the flea the trypanosome is confined 
throughout its whole development to the digestive 
tract, where it undergoes extensive asexual multiplica- 
tion and passes through a number of more or less 
distinct phases, some of which are intracellular in the 
epithelium of the stomach. No sexual phenomena 
have been detected, and the authors agree with Miss 
Robertson that such phenomena have not as yet been 
satisfactorily demonstrated in the case of any trypano- 
some. 

CHANGES OF RELATIVE LEVELS OF 
LAND AND SEA. 
GAN = the different kinds of evidence showing 
that changes in the relative levels of sea and 
land are going on all over the globe, the forms 
assumed by coast-lines are now recognised by geo- 
logists as being the most convincing and satisfactory. 
Sea-erosion, acting only along shore-lines, and sub- 
aerial denudation, operating over the whole land- 
NOm237/2, VOLES | 

surfaces, result in features of such clearly differ- 
entiated character that no unbiassed observer can fail 
to recognise their great significance and value. When 
we find long, narrow, deep, and winding inlets from 
the sea into the land (‘‘fiords,’’ etc.), it is obvious 
that such features could not result from the cutting 
back of the coast-line by the sea, but that they are 
old river-channels that have been drowned by the 
sinking of the land. On the other hand, sea-beaches, 
with caves, fan-taluses, and other signs of shore 
work, occurring at various heights above the present 
sea-level, speak, quite as unmistakably, of elevation 
having taken place. 
The illustrious American geologist, James Dwight 
Dana, when accompanying the United States Explor- 
ing Expedition under Wilkes, had the opportunity 
of visiting many coral-reef islands, and we are in- 
debted to him for first showing, in 1849, the value 
of the evidence afforded by coast-lines, where bounded 
by ‘encircling’’ or ‘“‘barrier”’ reefs, of subsidence 
having taken place. These valuable observations of 
Dana seem to have been almost completely over- 
looked until quite recent years, and it is only fitting 
that to a fellow-countryman of his should fall the 
task of recalling and developing this pioneer work. 
Where a coral-reef encircles a land-mass it is evident 
that the presence of ‘‘fiords” or their equivalents in 
the central island supplies clear evidence of submerg- 
ence having taken place, though possibly this may 
not be the latest of the movements that have occurred. 
On the other hand, the existence of islands composed 
of upraised coral-rock, with sea-caves and shore de- 
posits at different stages, up to more than 1000 ft. 
above the present sea-level, supplies equally clear 
evidence of movements in an opposite direction having 
taken place. The late Prof. Alexander Agassiz pub- 
lished a very valuable series of reports, abundantly 
illustrated, concerning these upraised Pacific reefs, 
and we now have the promise of equally important 
descriptions by Prof. W. M. Davis, also of Harvard, 
of the cases in which the proofs of subsidences can 
be no less satisfactorily made out. 
The general result to which these various observa- 
tions appear to point is that, over the whole area of 
the Pacific, areas of elevation and others of subsi- 
dence can be clearly traced, though the movements 
were often interrupted and sometimes reversed; never- 
theless, it must be admitted that in some cases the 
evidence seems puzzling and contradictory—islands 
with clear evidence of elevation lying in close 
proximity to others which have clearly subsided. 
Geologists will not, however, be unprepared for the 
occurrence of such seeming anomalies; they will only 
recognise that, eventually, actual fault-lines may be 
traced by such means in the oceanic areas. At the same 
time it may be well to bear in mind the caution sug- 
gested by Darwin in his correspondence with Semper 
that, however clear may be the evidence in favour of 
any special theory of coral-reef formation, we must 
be always prepared for the occurrence of special cases 
which can only be accounted for by the operation of 
exceptional causes. The full and complete account— 
which will no doubt be sufficiently illustrated—of 
Prof. W. M. Davis’s important series of explorations 
will be looked forward to with special interest, and 
in the meantime the subjoined general summary of 
his results will be welcomed by all naturalists. 
NW. J. 
Preliminary Report on a Shaler Memorial Study of 
Coral Reefs. 
A liberal grant from the Shaler Memorial Fund of 
Harvard University, supplemented by a generous sub- 
sidy from the British Association for the Advance- 

