116 
NATURE 
[ DECEMBER 3, 1903 
European genera are present in America, some are extremely 
rare, represented by a single species; others have a different 
range in America from that in Europe. These differences 
of range and association give hints as to the region where 
some of the forms originated, but the information is too 
indefinite to allow any positive statements as to the faunal 
geography of that time. The author, however, concludes 
that at least periodically there was easy intermigration 
between the American and the European waters, for the 
community of genera, and even of species, is too great to 
be explained by any other hypothesis. We note that 
Glyphioceras calyx, Goniatites crenistria, G. sphaericus 
and G. striatus are recorded from the Lower Carboniferous 
of America. The work is illustrated by twenty-nine plates. 
Monograph No. xliii. is on ‘‘ The Mesabi Iron-bearing 
District of Minnesota,’’ by Mr. Charles K. Leith. The iron- 
bearing formation occurs in the Upper Huronian, and in 
what is known as the Biwabik division. This comprises a 
variety of rocks, including slates, cherts, and ‘“‘ greenalite.”’ 
This last-named substance consists largely of minute 
granules of green ferrous silicate, without potash, and is 
named greenalite for convenience. The cherts and iron 
ores are shown to develop mainly from the alteration of the 
greenalite granules. Interbedded slate-rocks occur, and 
paint-rocks have resulted from their alteration. The iron 
ores are in basin-shaped deposits of considerable horizontal 
extension. Full particulars are given of these and of the 
methods of mining, while other rocks which enter into the 
structure of the district, the Archean, Lower Huronian, 
the Keweenawan gabbro, the Cretaceous rocks, and Glacial 
drifts are described. The work is accompanied by maps, 
pictorial views, and plates of microscopic sections. 
A series of Bulletins of the Geological Survey (published 
1902-3) has been received. No. 203 comprises the invalu- 
able “ Bibliography and Index of North American Geology 
for 1g01,’’ by Mr. F. B. Weeks; 866 works are listed, and 
they are for the most part accompanied by brief notes of the 
contents. In No. 191, also the work of Mr. Weeks, there 
is a list and references to *‘ North American Geologic Form- 
ation Names,’’ a work of unquestioned utility. We cannot 
help thinking that formational terms should, wherever 
possible, be derived from original place names. Even 
names like the Appotomax, Bearwallow, Caloosahatchie, 
Shawangunk or Wapsipinicon beds are preferable to those 
of Alnwick, Barnstaple, Falmouth, Tisbury and Tiverton 
beds, some of which have a meaning in this country. 
Other native names, such as the Anamosa, Keewatin, 
Shenandoah and Wyoming, and even the Mormon beds, are 
appropriate. 
No. 206 is a study of the fauna of the Hamilton 
(Devonian) formation of the Cayuga Lake section in Central 
New York, by Mr. H. F. Cleland. An attempt was made to 
collect the complete ‘‘ faunule’’ from each zone, and it is 
stated that the examination failed (with one possible excep- 
tion) to reveal any evolutional changes. The species are as 
distinct or as variable in one portion of the section as in 
another. Annarently it makes little difference how much 
time elapses so long as the conditions of environment remain 
unchanged. Some repetition of faunas is noted. 
In No. 205 Mr. G. B. Shattuck deals with the Mollusca 
of the Buda (Cretaceous) Limestone, and Mr. T. W. 
Vaughan deals with the corals. The work is accompanied 
by many plates of fossils. In No. 204 the fossil flora of the 
John Day Basin, Oregon, is described and illustrated by 
Mr. F. H. Knowlton. The beds which yield the plants are 
Eocene and Miocene. 
In No. 195 Mr. T. N. Dale contributes a second paper 
on structural details in the Green Mountain region and in 
eastern New York. Various structures in pre-Cambrian 
and Cambrian rocks, showing the complex interaction of 
mechanical and chemical processes, are described, and in 
one case the amount of shear is indicated by deflected 
annelid borings. 
Economic geology receives treatment in several Bulletins. 
No. 199, by Mr. I. C. Russell, is on the geology and water 
resources of the Snake River plains of Idaho. Many 
curious volcanic features are illustrated, including some 
volcanic bombs. No. 198 is on oil sand in Ohio; No. 200, 
on borax deposits in California, and No. 202 on gold and 
silver in western Kansas. In No. 207 there is an essay on 
the action of ammonium chloride upon silicates. 
NO. 1779, VOL. 69] 
Geography is illustrated in No. 196, wherein Mr. J. S. 
Diller treats of the topographic development of the Klamath 
Mountains in California and Oregon; in No. 197, by Mr. 
H. Gannett, on the origin of some ten thousand place names 
in the United States; and in No. 201, which contains results 
of primary triangulation. 
The Maryland Geological Survey, under the direction of 
Prof. W. B. Clark, sends two memoirs on the counties of 
Cecil and Garrett. These deal exhaustively with the local 
geology and topography, with the rocks igneous and 
stratified, the mineral resources, soils, climate, forests, &c. 
They are well illustrated and admirably printed, and with 
their colour-printed maps they may be regarded as in all 
respects models of what geological survey memoirs 
should be. H. B. W. 
WINTER WHITENING OF ANIMALS.? 
HE winter whitening of animals, though of intense 
al interest to zoologists, is very imperfectly understood 
Most writers are satisfied to believe that this colour change 
was perfected somehow under the action of natural selection 
for the protective purposes of adaptation to environment- 
Its origin they leave as an unsolved problem. ; } 
I find, however, that the change has a deep physiological 
significance. There is, for instance, in mammals a de- 
finite sequence in which the various parts of the body 
whiten. This sequence corresponds to the summer accumu- 
lation of fat in the panniculus adiposus. Thus the belly, 
where peripheral fat is thickest, is permanently white, and 
the rump, where also fat accumulates thickly, is usually the 
first part to whiten in winter. 
Many northern mammals and birds not usually regarded 
as of the winter-whitening category are lighter in winter 
than in summer. The whiteness or white patches assumed 
| in the former season correspond to the fat tracts, so that 
these species may be regarded as subject to the same process. 
In the northern summer most animals accumulate fat, 
always in a definite manner as regards the regions where 
it is deposited. This fat is indicative of deficient oxydisa- 
tion and of sluggish metabolism, and the process of its 
accumulation is therefore one of atrophy. The fat accumu- 
lation and atrophy are most marked in autumn, at which 
season metabolism is therefore lowest. With the onset of 
winter cold, the atrophy may extend to the hairs. Their 
pigment (as observed by Metchnikoff) is then removed, 
always, however, commencing with those parts where peri- 
pheral fat is thickest, and atrophy therefore greatest. 
Should there be a change of coat at this time, the new 
hairs are influenced by the same conditions. In very cold 
countries they come up white all over the animal; in more 
temperate regions the parts only where fat is thickest are 
white. 
Although a pigmented hair can thus undergo atrophy and 
loss of pigment, I know of no case where the colour is re- 
placed. Animals once whitened remain so until the spring 
moult. 
These facts apply broadly to birds and mammals, but the 
hare and stoat are the species which I have studied 
especially. 
Similar laws govern a great deal of the distribution 
of the white colour throughout the vertebrate phylum, 
wherein 
be widely traced. Thus domestic animals, nearly all of 
which are prized most for their power of accumulating fat, 
exhibit a strong tendency to the development of white 
patches. In both these and in wild animals the belly, where 
occurs the principal fat tract, is the most frequently white 
part; next follow the rump, and parts of the neck, of the 
limbs and of the head. 
Marked exceptions are, no doubt, frequently due to un- 
usual arrangements of the panniculus adiposus. Thus in 
the badger, a representative of a family in which the back 
is usually whiter than the belly, I find a correspondingly 
exceptional arrangement of the fat tracts. 
1 Abstract of a paper read before the Royal Irish Academy on May rr 
by (apt. Barrett Hamilton, on a physiological theory to explain the 
winter whitening of birds and mammals living in snowy countries, and the 
most striking points in the distribution of white in vertebrates generally. - 
the connection between white colour and the — 
peripheral fat tracts (thus indicating local atrophy) may 
ae 
