INFLUENCE OF THE EYES, EARS, AND OTHER ALLIED SENSE 
ORGANS ON THE MOVEMENTS OF THE DOGFISH, MUSTELUS 
CANIS (MITCHILL). 
j- 
By G. H. PARKER, S. D., 
Professor of Zoology, Harvard University. 
The common occurrence of the smooth dogfish, Mustelus canis (Mitchill), in the 
waters about Woods Hole, the success with which this fish can be kept in confinement, 
and the ease with which it resists the adverse effects of operations led me to undertake 
a study of its more important sensory reactions. This paper deals with the effects of 
the following sense organs on the movements of the dogfish: Eyes, ears, lateral-line 
organs, the ampullae of Eorenzini, and the organs of touch. The work was carried out 
at the United States Fisheries Laboratory, Woods Hole, Mass. 
CLASSES OF MOVEMENTS. 
The more obvious external movements of the dogfish fall into four classes. The 
first class consists of the movements of the eyeballs, either backward and forward, as 
for instance when the fish is swimming, or rolling movements such as occur when the 
animal is rotated on its long axis. The second class of movements are those of the false 
eyelid or nictitating membrane, which can be made to rise from the ventral edge of the 
orbit and thus cover the surface of the eyeball ordinarily exposed. The third class of 
movements are the respiratory movements of the gill region. These vary much in rate 
dependent upon the momentary state of the animal. In a large resting fish they vary 
from about 35 to 45 movements per minute. The same fish when swimming slowly will 
respire 50 to 55 times per minute. In vigorous swimming the rate is doubtless still more 
rapid. The fourth class of movements are the locomotor movements which are carried 
out in the main by the fins. The specific gravity of the dogfish is slightly greater than 
that of sea water and when the fish ceases to swim it sinks to the bottom. As it has no 
swim bladder, it is incapable of floating in the water as many teleosts do, and whenever 
it is off the bottom it maintains its position necessarily by active swimming. In this 
operation all the fins are concerned, but of these none is so important as the caudal fin. 
If one dorsal fin or the anal fin is removed, the fish swims apparently as well as ever. If 
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