204 BULLETIN OF THE BUREAU OF FISHERIES. 



away from the center of disturbance, so that I am led to conclude that the disturbances 

 set up by such an object as a stone falling into the water stimulate the lateral line 

 organs and with more or less directive effect, as surmised by Bonnier (1896). 



That the movements generated in the water by the male Poh/acanthus when 

 mating are stimuli for the lateral line organs of the female, as suggested by Stahr 

 ( L897), may be true, but is unsupported by any proof. 



So far as these observations go they show that surface wave movements, whether 

 produced by moving air on the water or solid bodies falling into the water, are accom- 

 panied by disturbances which are stimuli for the lateral-line organs. This doubtless 

 is the most usual form of stimulus for these organs in surface tishes, for I have 

 shown that currents and direct wave action are probably not effective in this respect. 



SUMMARY. 



1. The lateral-line organs are not stimulated by light, heat, salinity of water, 

 food, oxygen, carbon dioxide, foulness of water, water pressure, water currents, 

 and sound. 



2. The lateraldine organs are stimulated by water vibrations of low frequency- 

 six per second. 



3. The lateraldine organs may lie of service to the fish in orientation, but they 

 are of no more significance in equilibration than the skin, and are inferior in this 

 respect to the eye and the car. 



4. \Yaves on the surface of the water produced by air currents and the disturb- 

 ances made by bodies falling into the water produce vibrations in the deeper water 

 that stimulate the lateral-line organs. 



5. The skin, the lateral-line organs, and the ear form a natural group of sense 

 organs whose genetic relations are such that the skin (organs of touch) may be said 

 to be the first generation from which the lateral-line system has been derived, and 

 this in turn has given rise to the ear. 



LIST OF REFERENCES. 

 Allis. E. P. 



1889. The anatomy and development of the lateral-line system in Amia calva. Journal of Mor- 



phology, vol. 2, no. 3, pp. 463-566, pis. 30-42. 

 Ayeus, H. 

 1892. Vertebrate Cephalogenesis. II. A contribution to the morphology of the vertebrate ear, 



with a reconsideration of its functions. Journal of Morphology, vol. 6, no. 1, pp. 1-360, 



pis. 1-12. 

 Batesox, W. 



1890. The sense organs and perceptions of fishes; with remarks on the supply of bait. Journal 



of the Marine Biological Association, new series, vol. 1, pp. 225-256, pi. 20. 

 Beard, J. 

 1884. On the segmental sense organs of the lateral line, and on the morphology of the vertebrate 

 auditory organ. Zoologiacher Anzeiger, Jahrg. 7, no. 161. pp. 123-126; no. 162, pp. 

 140-143. 

 Beckwith, C. J. 

 1902. The early history of the lateral line and auditory anlages in Amia. Science, new series, vol. 

 15, p. 575. 



