PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. 223 
B. EXPERIMENTS AND OBSERVATIONS. 
I. The Otocyst as an Auditory Organ. 
That the responses of water-inhabiting animals to atmospheric sounds 
is nothing more than a myth, has been too well proved by Beer to need 
further investigation. The well-known physical fact that the larger 
part of the sound waves are reflected from a liquid surface is enough in 
itself to confute fables of fishes and crustacea hearing, and coming to be 
fed at the sound of a bell. But since in the case of responses of decapod 
Crustacea to sound vibrations conducted into the water, the experiments 
of Beer contradict Hensen’s earlier results, repetition of Beer’s work, 
though perhaps not absolutely necessary, may not be out of place. 
Metuops. 
The shrimps to be experimented upon (Palzemonetes) were placed 
in glass vessels 40 cm. in diameter and 20 cm. deep. Sound waves 
were conducted to the water by means of a steel pipe one inch 
in diameter and about two feet long, which was firmly clamped at 
its upper end and projected into the vessel containing the shrimps; a 
brass rod was in some cases substituted for the pipe. The pipe and rod 
were set into vibration either by striking them with a hammer, or by 
drawing across them, bowlike, a strap of rosined leather. Sounds were 
also produced by striking glass jars suspended in the water, and by 
striking the sides of the aquarium itself. The movements made in pro- 
ducing the sounds were completely screened from the view of the 
shrimps by pieces of cardboard placed over and at one side of the 
vessel, a small aperture being left for observing their reactions. 
Palzmonetes could be made very sensitive to all nervous stimuli by 
leaving them over-night in sea water containing from 0.1 to 0.2% of 
sulphate of strychnia. This solution is fatal to a small fish (Fundulus) 
in five minutes; many of the shrimps die, but the sensory apparatus 
of those which remain alive is rendered abnormally acute. Blinding 
was accomplished by simply painting the eyestalks with a thick coat of 
lampblack and shellac ; the otocysts were removed by means of a fine 
hooked needle, with scarcely any other injury to the animal. 
1. Responses of Paleemonetes to Vibrations transmitted to Water. 
a. Normal Conditions. Under normal conditions, when sound vibra- 
tions were transmitted to the water, normal animals responded by a 
