GOBIES AND MUD-SKIPPERS. 389 



geographical distribution as extensive as that of the family, but especially well 



represented in tropical and subtropical seas, no less than forty different kinds 



being recorded from those of 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. Jiuviatilis) 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 pole wig (67. 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 downwards, 



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 {Latnmcidus pdlucidus), 



belonging to a distinct genus, and characterised by its translucent bod}", 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 

 Mud- Skippers. . \ . 



genera, our next representatives or the family are the mud-skippers 



(Periophthahnus), 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 Burnished 



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 firsf dorsal fin includes 



