THE GOBIES AND MUD SKIPPERS 2759 



India alone. These fishes have the body generally scaled; two dorsal fins, of 

 which the first is usually furnished with six flexible spines; the pelvic fins united 

 to form a disc, which, however, is at most only partially adherent to the abdomen; 

 the teeth in more than a single row; and the vertical gill opening of moderate width. 

 The form of the body is subject to considerable specific variation; and in some 

 forms the head, and in others a part or even the whole of the body is devoid of 

 scales. In some cases there may be barbels or warts on the head, and in others a 

 crest on the occiput. There are likewise considerable differences in the dentition, 

 some species having large tusks among the ordinary teeth. The gobies, of which 

 there are several British marine species, are especially partial to rocky coasts, where 

 they protect themselves against waves and storms by adhering to rocks by means 

 of the sucker formed by their modified pelvic fins; many of them being often found 

 in the swirl of the retreating waves. Some, however, prefer brackish estuaries or 

 lagoons, while others again, like the Russian species (G. fluviatilis) represented in 

 our illustration, are exclusively fresh water. In many of them the male constructs 

 a nest in which the spawn is hatched. In the case of the spotted goby, or polewig 

 (G. minutus) a species found for some distance up the Thames the male when 

 in tidal pools, generally chooses one of the shells of a cockle or some other bivalve 

 for its nest; the shell being placed on the sand with its concave surface downward, 

 beneath which the sand is hollowed out and cemented by a special mucilaginous 

 secretion from the skin of the fish; a cylindrical tunnel giving access to the nest, 

 and the whole structure being covered over with loose sand. The female having 

 deposited her eggs, which are fixed to the shell, in this nest, the male mounts 

 guard over them, maintaining his watch during the whole period of incubation, 

 which lasts from six to nine days. A European goby (Lcttrunculus pellucidus) 

 belonging to a distinct genus, and characterized by its translucent body, is 

 almost peculiar among vertebrates in that its span of life is of only a year's 

 duration. In June and July the spawn is deposited, the eggs are hatched in 

 August, while in the late autumn or winter the fishes become fully mature; these, 

 however die off in the following July or August, so that in September only the fry 

 are to be met with. 



Omitting all mention of a number of more or less nearly-allied 

 s genera, our next representatives of the family are the mud skippers 

 {Ptriopkthcdmus) remarkable not only for the peculiar physiognomy given them 

 by their conspicuous eyes, but likewise on account of their strange habits. These 

 fishes, which frequent the coasts and estuaries bordering the Indo-Pacific Ocean, 

 and likewise reappear on the shores of West Africa, take their name from their 

 prominent eyes, which are set close together somewhat below the line of the profile, 

 and are not only capable of protrusion and retraction but are furnished with a well- 

 developed outer eyelid. The elongate body is covered with cycloid or slightly 

 pectinated scales, extending on to the bases of the pectoral fins; the cleft of the 

 mouth is nearly horizontal, with the upper jaw projecting somewhat beyond the 

 lower, and the conical teeth are vertical. The first dorsal fin includes a variable 

 number of flexible spines; the base of the pectorals are muscular; the pelvic fins 

 are united for a portion of their length; and the caudal fin has its lower border 



