OLFACTORY REACTIONS OF FUNDULUS 3 



the killifish, which carried on a vigorous competition as to which 

 should have possession of the packet. Frequently the first comer 

 would not only seize the packet and tussle with it, but would 

 often attempt to drive off other fish that had approached the 

 region, attracted apparently by the movements of the first fish. 

 These preliminary tests showed quite conclusively that the normal 

 killifish responds very quickly and in a characteristic way to 

 hidden food. 



It was also quite evident from these tests that the killifish, in 

 strong contrast with the catfish, uses its eyes as well as its chemical 

 senses, in seeking and retaining its food. If a small piece of dogfish 

 flesh is dropped into an aquarium in which there are hungry kil- 

 lifish, a fish is almost sure to pounce upon the piece and swallow 

 it quickly. This action is so sudden and begins when the fish is at 

 such a distance from the bit of flesh that it is evidently controlled 

 through the eye. That it is not entirely so, however, is seen from 

 the fact that if a small ball of clean filter-paper is thrown into the 

 water, this too is pounced upon and taken into the mouth but 

 soon discharged. Thus the sight of an object must be followed 

 by an appropriate stimulus of smell or taste, if the object is to be 

 swallowed. 



It is the eye, in my opinion, that leads killifish to swim to a 

 packet of plain cloth and seize it even though it contains no food. 

 The fact, however, that the fish do not remain about such a packet 

 long shows how clearly they distinguish it from a packet in 

 which meat is hidden and around which the}^ will gather and tussle 

 for long periods of time. The use of the eye in the prehminary 

 steps of the search for food is shown in the amusing habit that 

 these fish have of chasing drops of water down the glass face of 

 an aquarium as though the drops were bits of food. The eye, 

 then, in Fundulus is serviceable in the initial stages of procuring 

 food, but whether the material is to be persistently nibbled and 

 finally swallowed depends, as the preceding test shows, on other 

 senses than sight. 



Another feature in the reactions of these fishes that is of im- 

 portance in connection with their discovery of food and is 

 probably dependent chiefly on sight, is their habit of seeking food 



