FUNCTION OF LATERAL-LINE ORGANS IN FISHES. 199 



reaction can be called forth by touching the skin with the electrodes. If the lateral- 

 line nerve is cut on one side of the body and the electrodes are applied on that side 

 and at a point posterior to the cut, the pectoral-tin reactions that occur arc the same 

 as those seen when the lateral-line nerve is stimulated centrally. Since the pectoral- 

 tin reactions thus obtained disappear when the spinal cord anterior to the region of 

 stimulation is cut, there can lie no doubt that the general cutaneous terminations of 

 the spinal nerves are the recipients of the stimulus. Hence Lee's conclusion that 

 the lateral-line organs are organs of equilibration must be qualified by the statement 

 that there is no reason to suppose that these organs are more concerned with this 

 function than is the integument. This opinion is supported by certain observations 

 made by Lyon (1900, p. 7'.') to the effect that when the tail of a dog-fish is turned 

 laterally, compensating movements of the eyes can be observed even though the 

 second and eighth nerves are cut. Since these movements disappear on cutting the 

 spinal cord, Lyon concludes that the afferent path is from the sensory nerves of the 

 skin or muscle. 



So far as equilibration is concerned, the lateral-line organs are certainly much 

 inferior to the ear and even the eye. Thus if the nerves to the lateral-line organs of 

 a dog-fish are cut, the animal will continue to swim as a normal individual does. If 

 the eyes are covered, normal swimming still continues. Hut if the eighth nerve 

 of a dog-fish is cut. and the animal is made to swim rapidly, it will usually lose its 

 equilibrium even with the whole lateral-line system intact, and if the eyes are covered 

 it invariably does so. Thus while the eye may in part supplement the ear in orienta- 

 tion, the lateral-line organs seem to be of no significance in this respect, and our 

 only reason for supposing that the_v are of value in equilibrium is the fact that on 

 stimulating the lateral-line nerve, tin movements, etc., occur such as are produced 

 by stimulating the ampullar organs of the ear; but this does not raise them as organs 

 of equilibration to an order higher than that of the skin. Since in this respect they 

 are much inferior to the internal ear. it is misleading to designate them as special 

 equilibration organs. 



Vibrations of high frequency (sound). — The suggestion made by Emery (1880), 

 Mayser (1881), Bodenstein (1882), and others, that the lateral-line organs may be 

 accessory ears, calls for a test of these organs by sounds. To carry out this I used 

 the same apparatus that I had formerly employed to test the sense of hearing in fishes 

 (cf. Parker, 1903a, 1903b). This consisted of a marine aquarium, one end of which 

 was made of wood and in which was hung a smaller glass aquarium closed at one end 

 (that next the wooden end of the large aquarium) by a silk net of coarse mesh. Thus 

 the tish could be restrained in the smaller aquarium and yet be subjected to sound 

 from the sounding-board at the end of the larger one. As a source of sound I used 

 a tuning fork driven by electricity and giving out 100 vibrations per second. It was 

 placed on an isolated base so near the sounding-board that a very slight movement 

 was sufficient to bring it into contact with the board, and thus the sound could be 

 conveyed to the water. Experiments were made on Fundulus If t< /■<<<•/ 7 'tux, F. majalis, 

 St< notomus ch runup*, and MusteVus otitis. 



My experiments on Fundulus heterocUtus confirm my results of a year ago 

 (Parker, 1903a, p. 56; 1903b, p. 199). When normal individuals of this species were 

 stimulated by sound they often responded by pectoral tin movements and almost 



