NO. 180I MILLERS-THUMB AND ITS HABITS — GILL I07 



in which it is kept, but after such extraorcUnary exertions it sinks 

 down apparently exhausted to the bottom, and there for hours 

 remains motionless." 



Newman's observations have been corroborated by the present 

 writer. The attitudes and movements of the Millers-thumb are, in- 

 deed, very characteristic. They contrast with those of the perches 

 and minnows by their attachment to the bottom. There they will 

 remain for minutes and perhaps hours, motionless save for the res- 

 piratory movements of the gill and mouth — about 40 a minute. Gen- 

 erally they rest on the exserted ventral or anal rays and the body 

 is more or less tilted forwards and backwards. All the fins are 

 erect and motionless, and the pectorals outstretched sideways. The 

 eyes are lateral, but directed somewhat upwards, and they bulge on 

 each side of the interorbital area. The color is partly accommodated 

 to the ground on which the fish rests, and when that ground is gray- 

 ish sand, the color closely approximates, although the bands are 

 generally distinct. They are quite apathetic and may not be at all 

 disturbed by some other fish approaching and rubbing against them. 

 Sooner or later, however, one is impelled to move, and with a flirt of 

 the tail darts forwards. It rarely goes more than two or three inches 

 awav unless very much frightened. If induced to swim, it does so 

 bv a wriggling motion and laborious exercise of the pectoral fins.^ 



Another characteristic early (1856) insisted on by Newman is a 

 certain change of hues. "There is something very remarkable in the 

 changes of colour," and "these changes do not appear referrible to 

 the ordinary tendency which the colour of certain fishes has to as- 

 similate with the colour of the surface on which they are lying, but 

 extraneous causes produce the eft'ect ; the swallowing a worm, the 

 effort of a swimming adventure, and, on one occasion, the extrusion 

 of ova, have produced such changes that the fish could not have been 

 recognized under its altered aspect ; the colours are various shades 

 of gray and brown, and these are sometimes homogeneous, some- 

 times varied with great distinctness and brilliancy." Such changes 

 of color surprised Gage, who experimented "over and over again to 

 make sure there was no mistake." The change "from black to gray 

 takes place in five minutes and sometimes even less." The "cause 

 seemed" to Gage "to be the great fright and the light." Further, 

 "upon studying them more carefully in an aquariiun it was found 

 that when the water became deprived of its oxygen they would pant 

 like a suffocating animal, and become very pale, just as they did 



^ The observations of the present writer have been chiefly made on fishes in 

 aquariums at close range and repeated very recently (April, 1908). 



