PRENTISS: THE OTOCYST OF DECAPOD CRUSTACEA. PAT 
place only when the animal was within a few centimetres of the vibrat- 
ing surface, and was most marked when the antenne and antennules 
were in close proximity to it. After blinding the animals and removing 
their otocysts, no apparent difference could be detected in the reactions 
called forth, as compared with those of normal crabs; removal of the 
first two pairs of appendages caused, on the contrary, the responses to 
almost completely disappear. 
b. To Atmospheric Sounds. As the fiddler crab is on land a large 
part of the time, a number of experiments were tried to determine the 
effect of aerial vibrations upon them when they were feeding under per- 
fectly normal conditions. A position for observation was selected near 
a bank which was completely honeycombed by their burrows, where 
one could see the animals perfectly well, and yet be screened from their 
view by intervening bushes. If one remained perfectly motionless, the 
animals would come within a short distance of the observer’s place of 
concealment, feeding as unconcernedly as if no one were near. Whena 
number of crabs were little more than five feet distant, a horn was blown, 
care being taken to direct it away from them. Although a sound was 
thus produced loud enough to be heard at some distance, all the animals 
continued to feed undisturbed. 
The striking together of two stones, and the sound produced by strik- 
ing an iron pipe with a stone (the objects in both cases being held in 
the hand) also had no effect upon them. On striking the ground with 
a heavy stone all the crabs within a radius of ten or twelve feet were 
startled ; some of them merely stopped feeding, while others scuttled 
into their burrows. The same result was brought about by simply 
stamping upon the ground. If a quick movement was made in the 
sight of the animals, they at once scattered precipitately to their holes. 
These observations were repeated a number of times, and on crabs of 
two different localities, with the same results. 
From these experiments and observations, we may draw the conclusion 
that the fiddler crab, whether in water or on land, does not respond to 
true sound-stimuli, but is affected only by jars or vibrations transmitted 
to the water or to the ground. In neither case can they be said to hear. 
When feeding upon land they do not depend upon an anditory sense to 
protect them from terrestrial enemies, but rely entirely upon their keen 
vision and delicate tactile organs. 
The statement is generally accepted, that all animals which produce 
sounds also have a sense of hearing, and this is advanced as an argu- 
ment in favor of audition in Crustacea. The two well-known examples 
