514 FLYING FISHES AND THEIR HABITS. 



upon the air-bladder already noticed. The muscles are two for each 

 lobe, a large intrinsic and a small extrinsic muscle. The nervous 

 impulses are communicated to them by the last pair of cerebral nerves. 

 The intrinsic muscles, by contraction, produce vibratory quiverings 

 (fremissements) which, reinforced by the bladder, become sonoro-us 

 vibrations easily perceptible. These muscles, contracting while 

 they vibrate, may change the shape of the bladder, stretching or relax- 

 ing such or such a part of the organ of this flexible sounding-board 

 (instrument de renforcement), and by such changes modify the 

 several qualities of sounds. The whole subject has been discussed at 

 great length by Du fosse in his memoir on the sounds produced by 

 European fishes, jiublished in the Annales des Sciences Naturclles in 

 1874. In this article those Avho may be especially interested in the 

 subject will find explanatory details. (See especially 5. serie, t. 20, 

 article 3, pp. 47-51, 07, 08, 76, 80-81.) 



But the air-bladder with its accessories is not the only sound- 

 producing organ. The peculiar modifications of the suborbital bones 

 and opercular apparatus are associated with a peculiar function — a 

 stridulation which may be distinctly heard at a considerable distance. 

 The pontinal or third suborbital bone is articulated so that it can 

 be bent at a right angle with the enlarged second, and when the 

 spiniform preoperculum is flexed outward the little pontinal is 

 extended across and at a right angle between the reentering angle of 

 the preopercular sinus and the second suborbital. "^Mien the pre- 

 opercle is depressed and pushed forward and inward, its anterior 

 articular surface grates upon the hinder angle of the lower jaw, and 

 a distinct stridulatory sound is produced, reminding one of the 

 strident notes of orthopterous insects, such as crickets or locusts, and 

 grasshoppers. Attention was called to this fact and a full explana- 

 tion given by W. Sorensen in 1884. 



IV. 



Oviposition probably occurs in the spring and the eggs are doubt- 

 less cast and fertilized near the surface of the Avater, and there 

 the earliest days of the fish's life are spent. The earliest stages are 

 unknown, but it is in the postlarval growth that the greatest inter- 

 est is centered. Allien, or rather before, the young has acquired a 

 length of a third of an inch, it has a helmet whose posterior processes 

 reach as far back as the soft dorsal and the preopercular spines 

 extend to the anal ; at the same time the pectoral fins are short and 

 entire, and the spinous dorsal little developed. This condition, so 

 dift'erent from that niajiifest in maturity, continues, but with dimin- 

 ishing dispr()])ortion, till the length of nearly or quite 2 inches has 

 been attained. Fishes possessing these characters were believed by 

 the old ichthyologists to represent a peculiar genus, to which the 



