ZOOLOGY. 237 
_ turns in the direction of that antenna which is most strongly 
shaken, The fibrils on the other antenna are now shaken with 
more and more intensity, until, haying turned his body so that both 
antenne vibrate with equal intensity, he has placed the axis of his 
body in the direction of the sound. Experiments under the micro- 
scope show that the mosquito can thus detect to within five degrees 
the position of the sonorous centre. To render assurance doubly 
sure, Prof. Mayer, having found two fibrils of the antenn of a 
mosquito which vibrated powerfully to two different notes, measured 
these fibrils very accurately under the microscope. He then con- 
structed some fibrils out of pine wood, which, though two or three. 
feet long and of the thickness of small picture-cord, had exactly 
the same proportion of length to thickness as the fibrils of the an- 
tenn of the mosquito. He found that these slender pine rods or 
-fibrils had to each other the same ratio of vibration as the fibrils of 
the mosquito. 
> 
CHANGE or HABIT.—A]l who have travelled of late years on the 
St. John’s River, in East Florida, must have noticed the cows 
Standing for hours at considerable distances from the shore, 
thrusting their heads from time to time into the water. This 
_ is explained by a change of habit to which they have been driven, 
during the winter months, by a scarcity of suitable grazing on 
land. Grazing is never very. good there at any time and compels 
them to feed on moss, young palmetto leaves, shoots of shrubs, 
ete., which under ordinary circumstances they would reject. The 
“river grass,” which appears to be a-species of Valisneria, has 
become a new and very considerable resource for food. It is said 
that this plant has established itself, within a few years, in the shoal 
waters of the lower part of the St. John’s where it now covers large 
_ Submerged tracts, and it is to obtain this that the cows have taken. 
to their semizaquatic habits. We have frequently watched them 
and have found that while gathering food, the head was kept be- 
neath the surface for a period varying from fifteen to thirty-five 
Seconds, during which time respiration was of course averted. We 
have recently seen a colt feeding in a similar manner. The hogs 
have also taken up this habit, but hold their heads under the 
water for a-shorter time than the cows. The young calves, though 
they do not eat the “ grass,” follow the cows and may sometimes 
YMAN. 
be seen with their heads only out of wáter.—I. J. W 
