120 
Notices of Books. 
[January, 
in others they are fully developed. In Ethusa granulata, 
a stalk-eyed crustacean, well - developed eyes are found in 
specimens taken in shallow water. In deeper water, from 
no to 370 fathoms, the eye-stalks are still present, but the ani- 
mal is apparently blind, the stalks ending not in eyes, but in 
mere round calcareous knobs, whilst at still greater depths, from 
500 to 700 fathoms, the eve-stalks themselves lose their specific 
character and become fixed. Here, then, as the author remarks, 
we “ have a gradual modification, depending apparently upon a 
gradual diminution and final disappearance of solar light.” But 
in Munida , a form from equal depths, the eyes are “ unusually 
developed, and apparently of great delicacy.” 
It is certainly conceivable that as the light gradually decreases 
in amount one of the changes may take place ; the power of 
vision may fade away pari passu as no longer needed, and its 
organs themselves may ultimately become abortive, or, on the 
other hand, it may become more and more acute as the solar 
light declines, and, as Sir Wyville Thomson suggests, may 
“ become susceptible of the stimulus of the fainter light of phos- 
phorescence.” But on what does it depend in any given case 
which of these two kinds of progressive modification shall take 
place ? Why do we find the influence of identical circumstances 
so different, if not diametrically opposite ? This is a question 
which the biologist has often to put to himself in vain. 
A most interesting phenomenon met with in the Falkland 
Islands may require a somewhat lengthened notice on account 
of its connection with the “ glacial question.” We refer to the 
so-called “ stone-rivers,” a natural feature not occurring else- 
where on such a scale. Many of the valleys in the East Island 
are occupied by pale grey masses, varying in width from a few 
hundred yards to a mile or upwards, and which, from a distance, 
simulate glaciers descending from the ridges and stretching down 
from the sea. They consist, however, not of ice, but of blocks 
of quartzite, from two, twenty feet in length by about half as much in 
width, resting irregularly upon each other, and supported by the 
edges and angles of those below. They are not weathered to any 
extent, though the edges and points are in most cases slightly 
rounded, and the surface also perceptibly worn, but only by the 
aCtion of the atmosphere, is smooth and polished, and a very thin, 
extremely hard white lichen, which spreads over nearly the 
whole of them gives the effeCt of their being covered with a thin 
layer of ice.” Water is heard murmuring down below, and occa- 
sionally becomes visible where the interval between the blocks 
is exceptionally large. At the mouth of the valley the seCtion 
of the “ stone-river ” is like that of a large stone drain. The 
only difficulty in accounting for this phenomenon is, according to 
the author, the slightness of the slope ; that from the ridge to 
the valley not exceeding six degrees, whilst the inclination of the 
valley itself is only two or three, so that blocks of such a form 
