March 12, 1897.] 



SCIENCE. 



427 



Nocturnal and diurnal changes in the color of 



certain fishes, with notes on their sleeping 



habits. A. E. Verrill. 



While investigating the nocturnal habits 

 ■of fishes, etc., in the aquaria of the labora- 

 tory of the U. S. Fish Commission, at 

 Wood's Holl, in 1885 to 1887, I unexpect- 

 edly discovered that many species of fishes, 

 and also the common squid {Loligo Pealei) 

 iake on special colors at night, while asleep, 

 ■or at rest, in a feeble light. These obser- 

 vations have not hitherto been published, 

 because I hoped to have had opportunities 

 to continue them and make them more 

 complete. It is now my hope that others, 

 with better opportunities, may take up the 

 subject. My observations were made after 

 midnight, when everything was quiet, for 

 fishes sleep very lightly. The gas jets 

 near the aquaria were turned down as low 

 as consistent with distinct vision, and 

 great care was taken not to jar the floor or 

 furniture. With these precautions I was 

 able to detect many species in the act of 

 sleeping. Some of them took unexpected 

 positions when asleep. 



The most common change in colors of 

 the sleeping fishes consisted in a general 

 darkening of the dark spots, stripes or other 

 markings, by which they become more dis- 

 tinct and definite. This was the case with 

 various flounders, minnows {Fundulus) , the 

 black sea-bass (Serranus furvus), the sea- 

 robins (Prionotus evolans and P. pahni2)es), the 

 king-fish (ilentieirrus nebulosus) and several 

 other species. 



In all these cases the change of color is 

 in the direction of increased protective 

 coloration, the dark markings being gener- 

 ally connected with their habits of resting 

 naturally at night among eel-grass and sea 

 weeds. The young fishes often showed 

 greater changes than the adults. 



Other species showed a much greater 

 ■change in color, for the pattern of coloration 

 was itself entirely changed. Thus the com- 



mon scup, or porgy (Stenotomus chrysops') , 

 while active in the daytime, is of a beautiful 

 silvery color with bright, pearly, iridescent 

 hues. But when asleep it takes a dull 

 bronzy tint and is crossed by about six con- 

 spicuous, transverse, black bands, a colora- 

 tion well adapted tor concealment among 

 eel grass, etc. If awakened by suddenly 

 turning up the gas, it almost instantly takes 

 on its silvery color, seen in the daytime. 

 This experiment was tried many times. 



A common file-fish (Monacanthus) , which 

 is mottled with dark olive-green and brown 

 in the daytime, when asleep becomes pallid 

 gray or almost white, while the fins and tail 

 become black. These are nocturnally pro- 

 tective colors. The file-fishes, when asleep, 

 often lean up obliquely against the glass of 

 the aquaria, with the belly resting upon the 

 bottom in very queer positions. The tautog, 

 or black fish {Tautoga onitis), commonly 

 sleeps on one side, often partly buried in 

 sand or gravel, or under the edges of 

 stones, much after the fashion of flounders, 

 thus suggesting the mode in which the 

 flounders may have developed from sym- 

 metrical fishes in consequence of this mode 

 of resting, becoming chronic as it were. 



Notes on the Phylogeny of the Carnivora. W. 

 B. Scott. (Read by title.) 



The Peripheral Nei'vous System of Nereis Virens. 



F. E. Langdon. 



This study was made partly on material 

 living and unstained ; partly on that stained 

 by methelene blue and examined either 

 fresh or fixed by Bethe's method, and partly 

 on_ that prepared by the more common 

 methods. 



The spindle-shaped sensory cells de- 

 scribed by Eetzius as isolated are really 

 grouped into semi-organs which have a 

 definite distribution over the body. Each 

 organ consists of a fusiform group of cells 

 whose bodies lie below the epidermis or in 

 its base. The cuticular markings over the 



