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-kuown physical fact that the larger 

 part of the sound waves are reflected from a liquid sui-ftice 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 Heuseu's earlier results, repetition of Beer's work, 

 though perhaps not absolutely necessary, may not be out of place. 



Methods. 



The shrimps to be experimented upon (Palsemonetes) 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 loug, 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. 



Paloemonetes 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 

 1 mipblack and shellac ; the otocysts were removed by means of a fine 

 hooked needle, with scarcely any other injury to the animal. 



1. Responses of Paloemonetes to Vibrations transmitted to Water. 



a. Xormal Conditions, Under normal conditions, when sound vibra- 

 tions were transmitted to the water, normal animals responded by a 



