Color Discrimination in the Gray Snapper. 269 



tlian a single experience with any one sort of modified atherina. The evi- 

 dence, therefore, does not show that the snappers do not learn by experience ; 

 it shows merely that they try every new possible-food object that comes into 

 the environment. This fact that the behavior of the snappers has yet to be 

 adjusted to each particular kind of new food is itself of importance in con- 

 nection with the theories of warning color and mimicry. The snappers 

 have, for instance, formed no habit of rejecting food of a particular color. 

 So far as concerns new possible-food they are still in the condition of the 

 young chick which pecks at all sorts of small, near objects. That the be- 

 havior of the snapper may be rapidly adjusted to new qualities in its food 

 appears in a later section of this paper. The necessity of such constant food 

 adjustments is clear when we remember that the snapper increases many 

 thousand-fold in bulk in its growth from the egg to the adult condition. 

 Between the minute forms which must serve as the food of the very young 

 fish and the larger forms upon which the piscivorous adults feed there is 

 a wide gap, which must be bridged in the food of the growing individual. In 

 the process of adjustment of the individual snapper a warning-color reaction 

 may conceivably be established and may then be utilized by a mimicking form. 



V. COLOR DISCRIMINATION IN THE GRAY SNAPPER. 



EXPERIMENT.\L METHODS EMPLOYED. 



It has been shown (table i) that gray snappers take without hesitation 

 red, yellow, green, blue, and purple atherinas, one with as much readiness 

 as another. There is thus suggested the possibility that these fish may be 

 unable to discriminate colors,' an inability which would, if common to the 

 predaceous fish of the reefs, be fatal to the theory of warning coloration. To 

 test the color-vision of the gray snapper the laboratory colony was fed on 

 dead atherinas that had been artificially colored. The natural silver-white 

 color of the atherinas and the almost complete lack of pigment in the dermis 

 makes it easy to dye them of a nearly uniform color. In addition to the 

 normal white atherinas there were used red, yellow, blue, and green fish of 

 light and dark shades. 



The snappers were first fed on atherinas of one color until they had 

 become familiar with that color and were then ofTered a choice between 

 that color and another and unfamiliar color. Choice was offered by throw- 

 ing ID atherinas together from the dock to the assembled snappers, 5 of 

 the familiar color and 5 of an unfamiliar color. The order in which 

 they were taken was recorded, so as to learn whether the snappers showed 

 power of color discrimination by taking first the fish of the familiar color 

 and last those of the unfamiliar color. Each throw of 10 atherinas is called 



'At the time these experiments were begun I knew of no experimental evidence 

 that fish distinguish colors. Since then Washburn and Bentley (1906) have published 

 an account of experiments on tlie minnow Sciiiolilns alromaculatus, which appears 

 to show color discrimination in a single individual of this species. 



