412 FRANCIS B. SUMNEE 



though changes of color tone, both adaptive and non-adaptive? 

 have been discussed by a large number of writers. That changes 

 of the former class actually occur will be evident to anyone who 

 devotes a moment to the inspection of my figures. Indeed they 

 are, in many instances, so striking that it is impossible to believe 

 that they have been wholly overlooked in the past.** 



The fish from which I obtained the most favorable results was 

 a small species of flounder, Rhomboidichthys podas (Delaroche)^ 

 belonging to the Psettinae or turbot tribe. This species occurs in 

 various parts of the Mediterranean Sea, but unfortunately it is 

 not so common in the Bay of Naples as one might desire for experi- 

 mental purposes. Less than forty ^^ specimens were at my dis- 

 posal during a period of about four months ; and during the latter 

 part of my stay the supply gave out completely. For this reason, 

 certain important tests were left untouched. 



Two larger species of turbot. Rhombus maximus (Linn.) and 

 R. laevis Rondelet, were used in a limited number of my Naples 

 experiments ; and gobies and several species of soles were likewise 

 tried, but without any results worth recording. 



At Woods Hole, my observations have been confined almost 

 wholly to the common 'sand-dab' or 'window-pane,' Lophopsetta 

 maculata (Mitchill), which, like Rhomboidichthys, is a represen- 

 tative of the turbot group. Casual observations upon the 'sum- 



ningham's "Treatise on the Common Sole," (Plymouth, '90, part iii, chapt. iii)' 

 The author here describes and figures a spotted condition which is said to be 

 manifested by this fish upon bottoms of gravel; but he later asserts: "All the 

 changes are evidently due to the action of light and depend on the quantity of 

 light acting on the sole, not on the tint or texture ofthe ground on which it rests." 



* Townsend (op. cit.)mentionsandfigurescasesin which the markings of various 

 fishes appeared and disappeared under different conditions; and Pouchet (op. cit., 

 p. 81-82) had earlier described a conspicuous, but apparently non-adaptive, 

 change of color-pattern in Callionymus lyra. Indeed certain instances of this phe- 

 nomenon are doubtless familiar to many persons, but most of such changes prob- 

 ably do not have any adaptive significai-ce. 



^ This species was one of those employed by Van Rynberk (op. cit., p. 549). 

 Strangely enough, he makes no mention (at least in the work cited, which alone is 

 accessible to me) of the extraordinary changes of pattern displayed by this fish. 



'" Of these a considerable proportion died within tns first few days of captivity. 

 Some specimens, on the other hand, lived for many weeks, and from such my best 

 ,.esults were obtained. 



