No. 389.] REVIEWS OF RECENT LITERATURE. 431 
organisms ” from the plankton for the detection of oceanic currents, 
especially with changing shore conditions, should be chosen with care. 
C A K. 
PHYSIOLOGY. 
Ocular Accommodation. — For several years past Dr. Theodor 
Beer,’ of the University of Vienna, has been investigating ocular accom- 
modation in those animals which possess well-developed camera eyes, 
and has presented in a lecture before the Fourth International Con- 
gress of Physiologists an admirable survey of this subject. According 
to him such water animals as the dibranchiate cephalopods and the 
bony fishes possess eyes which in the resting condition are accom- 
modated for short distances, and which require active accommodation 
for vision at long distances. This is brought about by shifting the 
lens, without changing its curvature, from a distant position to one 
nearer the retina. In the cephalopods this shifting is accomplished 
by the contraction of a ring-shaped muscle which works against the 
deeper contents of the eyeball. In the bony fishes a band-like 
muscle, the retractor of the lens, draws that body inward toward the 
retina. 
In the air-inhabiting vertebrates the resting eye is accceniucdaakd for 
distant vision. Near vision is possible only by active accommoda- 
tion. This is accomplished in one of two ways: either the lens, 
unchanged in form, is moved away from the retina, as in amphibians 
-and most snakes, or the convexity of the outer surface of the lens is 
increased, as in a few snakes, the turtles, crocodiles, lizards, birds, 
and mammals. The outward movement of the lens is brought about 
by an increase of pressure in the vitreous humor, produced by muscular 
contraction; the change in the convexity of the lens is induced by the 
well-known indirect action of the ciliary muscle. 
In all the groups of animals examined, with the exception of the 
cephalopods and the birds, some species were found in which accom- 
modation was entirely or almost entirely absent; such, for instance, 
was the case in the cartilaginous fishes, the sea eels, haddock, frogs, 
toads, salamanders, alligators, some lizards, vipers, and many rodents. 
Many of these are night animals, and possess in the daytime so small 
1 Beer, T. Die Accommodation des pate in der Thierreihe, Wiener klini- 
schen Wochenschrift, Nr. 42, Jahrgang 1 
