DOUBLY-SPOTTED (iOUV. 



2o5 



tlint in this case tlic adaptation takes place in a much 

 more i!itri(;ate manner, hut is always fruided by the 

 simple or variegated colours of the suri'oiindings. It 

 is often very Imrd to discover one of these fishes, when 

 at rest among tiie \\ater-])lants. 



"During autumn and winter the coloui's of the 

 Doubly-Spotted (iohy are duUei-, and the sexual distinc- 

 tion in this respect less marked. Furtliermore, different 

 individuals seem to possess the power of changing co- 

 lour in different degrees. One fisli takes twice as long 

 as another, before it acquires a uniform dark or light 

 colour; one retains a colour fairly (though never com- 

 pletely) utichanged for a long time, while another, 

 though on tlie same bottom and under the same cir- 

 curastances, seems to undergo an incessant shifting of 

 colour. If \\e continue the above experiments for a 

 lengthy period of time upon the same fish, the chro- 

 matophores become distinctly fainter." 



Most of the colour characters given in the aljove 

 description are, however, not entireh' peculiar to the 

 Doubly-Spotted Goby. The selliform spots, in particular, 

 ha^e been described as characteristic of the next t\vo 

 species, especialh' of G(U)ii(s 2>/cfi(s, and also occur, as 

 LiLLJEHoiic has already remarked, in (joJ)it(s mimifus, 

 even though some difference may l)e shown in their 

 prominence and position. The black caudal spot is also 



common to the following species, though in them it but, on leaving its resting-place, has risen in the water 



to discover in a(|uaria whicli are thickly overgi'own 

 with plants. It sustains life without difficulty in fresh 

 water, if gradually accustomed to it; but if suddenlv 

 remo\cd i'voni salt water to cold fresh water, it be- 

 comes rigid and dies with exjiandefl tins, just as when 

 it is thrown into strong spirit immediately after its 

 capture. LowK states of this species, according to Day, 

 that it readily learnt to take food from his hand. "Its 

 movements," says Heincke, "are restless and active; and 

 with the funnel-shaped ventral fins it can firmly attach 

 itself even to the perpendicular walls of the aquarium." 

 in its free state the Doubly-Spotted Gol)\- prefers 

 a I'ockv l)ottom, thickly overgrown with seaweed, at a 

 depth of tVom 1 to 10 fathoms; l)ut it is also found 

 in weedy spots, where the bottom consists of stones or 

 gravel. The Royal .Museum possesses several specimens 

 which were taken in a dredge at spots of this nature. 

 Malm, however, as well as Parxell, found it living in 

 quite another manner, more resembling the life of the 

 Sticklebacks. "In contradistinction to all the Gobies," 

 writes Malm, "whicli in Sweden keep to water so shallow 

 that they may be observed without difficulty, it is only 

 very seldom that this tish is seen near, or, more strictly 

 speaking, at the bottom. I ha\e observed this on only 

 fcM' occasions, and it lias then Ijeen a solitar^■, full- 

 grown male that has swum in and rested on a rock; 



seems never to be so sharply defined; and though the 

 emerald spots on the sides, sometimes sharply separated 

 bv a black space between them, have not been observed 

 in the following species, they still have a corresponding 

 marking of black, simple or bisected spots, which some- 



not creeping, as it weve, along the bottom like Gobivx 

 niger, microps, pkius and miiuitus. As a rule it is 

 only seen in larger or smaller, close-packed companies, 

 in mid-water, so to speak, and especially at clear spots 

 in the Zostera region. The water may be two or three 



times appear like transverse bands. x\s is shown in ! fathoms deep or more, but the shoal stays, sometimes 



V. Wright's figure, there also occur in Gobii(S _ffrirescens 

 two black spots, starting from the eyes down the cheeks 

 and snout, the one ending just behind the corner of 

 the mouth, and the other running almost straight for- 



almost still, a foot or two below the surface. I have 

 often seen shoals containing several hundred small spe- 

 cimens and only one or two full-grown individuals, 

 thus seeming to be composed of a family or two that 



ward. We may hence judge how inconstant are the led an isolated life in this manner. When disturbed, 



characters derived from colour; l)ut the black spot, the shoal sinks deeper in the water, l)ut as a rule, 



during life with an azure lustre, that occurs at the end soon rises again. I have never succeeded in enticing 



of the dorsal fin in the tw(j following species, and which this tish to take a bait, though I have taken its kin- 



Heixcke has given as one of the external sexual char- 

 acters of the male of (iohiiifs iiilnutns, is apparently 

 wanting in Gobliis ^fiarcsceiis. 



The habits of the Doubly-Spotted Gob}- are no less 

 interesting than its beauty of colour. It is one of the 

 most handsome aciuarium fishes and pleasing enough. 



dred species in this manner; liut when it leaves the 

 bottom, at least in the daytime, it may easily be taken 

 with a hand-net. ' 



The spawning-season occurs in summer, from 

 May to .\ugust. The female attaches the eggs to the 

 shells of dead shellfish or Balanids, and the male keeps 



though its propensity of hiding itself renders it difficult faithful and coui-ageous guard over them. 



