808 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxvni. 



body may be thrown outward at v^arious angles and even downward 

 and the tail wound around a plant in a double coil. Once in a while 

 one eye may roll toward you, while another ma}^ be passive or look 

 backward or in an op[)()sitc diivction. It ])ecomes obvious that the 

 little tish can move its eyes independently of each other and in entirely 

 di tie rent ways. 



A comical effect is pi'oduced by the way in which the little fishes 

 peer at some object, reminding one of the actions of a very near- 

 sighted person. 



Releasing itself at length from its support, one may slowly progress, 

 still in a vertical position, its tail curved inward, its dorsal tin rapidly 

 undulating and reminding one of a screw propeller, its pectorals 

 vibrating in harmony. The I'apidity of the undulatory or vibratory 

 movements of the dorsal and pectorals is especially noteworthy. 



Incased as it is in an almost inflexible coat of mail, progression can 

 not be effected by lateral flexion of the body as in ordinary fishes, and 

 flexion in a vertical direction is limited. 



With such limited powers of progression, a nice adjustment of organs 

 is called for, and Dufosse has explained one method. The air bladder 

 is comparatively large and always distended by a quantity of gas so 

 exactly in harmony with the specific gravity of the bod}' that this 

 entire body is a hydrostatic appai'atus of extreme sensibility. A proof 

 of this is that if a single ))ul)l)le of gas no larger than the head of a 

 very small pin be extracted, the hsh inuuediately loses its equilibrium 

 and falls to the ground, on which it must crawl till its wound has been 

 cicatrized and a new supply of gas secreted by the internal membrane 

 of the l)ladder. 



III. 



Another noteworthy peculiarity is a faint sound which is sometimes 

 evoked. Kent, while making '"some colored sketches'' of the fishes, 

 had two "isolated in separate glass receptacles some few yards apart, 

 when unexpectedly a sharp little snapping noise was heard at short 

 and regular intervals to proceed from one of the vases placed on a side 

 table, and to which a response in a like maimer was almost immedi- 

 diately made from the vase close at hand. On seeking for the cause, 

 the sound was found to proceed from the mouths of the little Ilippo- 

 camp!., which were thus conversing with, or signaling to, one another. 

 The noise observed was produced by the muscular closing and sudden 

 expansion of the lower jaw. and much resembled in strength and tone 

 the snapping sound produced for a similar purpose, but in this 

 instance with its claw, ])v the little scarlet prawn {Alpheus riihei')^'''' 

 relatives of which occur along the southern coast of the United States. 



The mechanism which produced the sounds emitted by the sea horse 

 was explained at length hy Dufosse in 1874 to whose memoir refer- 

 ence may be made by those who wish to learn details. Suffice it here 



