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BULLETIN OF THE UNITED STATES FISH COMMISSION. 
The rates at which some of these reactions were carried out are not without 
interest. In one set of experiments the females were made to descend 15 centi- 
meters from the surface by means of the opaque hood. From the time the hood was 
put on, which presumably marked the beginning of the descent, till the arrival of 
the animals below, was exactly 30 seconds. This indicated a descent at the rate 
of half a centimeter per second, which has already been shown to be the rate of 
passive falling. So far as one could judge from the first sight of the animals as they 
emerged below the level of the hood, they did descend by falling and not by any 
form of positive locomotion. It would, therefore, seem that diffuse daylight from 
below acts on female Labidocerse rather as an inhibiter of their negative geotropic 
reactions than as a positive phototropic influence. On the removal of the hood the 
females returned to their original position, but required 14 minutes to perform this 
migration. They thus descended three times as rapidly as they ascended — i. e., if 
they can descend a fathom in about 6 minutes they could probably not make that 
ascent in less than 18 minutes. 
In another experiment five female Labidocerse were put in a glass tube, of large 
caliber and about 50 centimeters long, and hung vertically in a dark chamber. When 
an incandescent electric lamp (14-candle power) was brought near the side of the 
tube, the five animals crowded close to it. When the lamp was held at the top they 
all ascended to the top, and they could easily be induced to descend through 50 centi- 
meters of water by holding the lamp under the bottom of the tube. Their descent 
was accomplished chiefly by passive falling, with the anterior end uppermost, though 
now and then they swam downward, an unusual action for a female. In this experi- 
ment, as in former ones, the responses of the females to gravity were always subor- 
dinate to those to light — i. e., geotropism was less pronounced than phototropism. 
A curious relation between these two sets of reactions was seen in the following 
experiment. The large tube, graduated to 10-centimeter intervals, was filled with 
sea water to the 50-centimeter mark; into it were put five females and the apparatus 
was covered with an opaque hood from the top to within 5 centimeters of the bottom. 
In this lowest section of 5 centimeters all the females congregated. The hood was 
now taken off in sections, beginning at the top. First, the top with 5 centimeters of 
the side covering was removed, leaving the tube covered for a distance of 40 centi- 
meters, beginning at 5 centimeters from the bottom. On thus illuminating the 
interior of the tube from above, it might have been expected that the five females 
would have risen through the dark section to the now light top; they, however, 
remained at the bottom. The uppermost 10 centimeters of the side covering were 
next removed, leaving 30 centimeters still covered, but without effect on the animals. 
The next lower 10 centimeters were now taken off:', leaving 20 centimeters covered, 
whereupon four of the Labidocerte immediately swam upward through the dark 
section to the light at the top. On removing the next 10 centimeters of the side 
covering the fifth animal ascended. Thus it appears that a dark region between a 
light top and light bottom may prevent female Labidocerge from ascending, an opera- 
tion, however, that they may perform before all the dark section has disappeared. 
The experiments on light thus far described make it clear that the phototropism 
of the male Labidocerge is at most slightly negative, that of the females strongly 
positive. So far as these facts are concerned they seem to have little bearing on daily 
migrations, for the slight negative phototropism of the males is not sufficient to over- 
