HAVE FISHES MEMOEY. 385 



teristic cf the phenomena described above as " tropisms." Plants and 

 the lower animals never vary their behavior toward light, heat, etc. 

 Likewise a number of so-called simple reflexes follow, with approxi- 

 matelv the same reg-ularity, instantaneously upon the irritations pro- 

 ducing them. The question is whether so low an order as fishes can 

 acquire or whether they possess reflexes that can be modified, inhibited, 

 or hastened by new sensations. Can impressions new to the animal 

 exercise influence upon its conduct? Above all, can they maintain 

 this influence for any length of time? 



A peculiarity present in even the youngest brood of fish is a recoil 

 from sudden optical or other -light impressions. 



This "flight reflex," as we shall call it for the sake of brevity, is 

 retained by all fishes bej' ond the stage of maturity. It can be height- 

 ened — ''the fish are timid;" it may be lessened — "the fish are getting 

 tame.'' That fishes grow tame is reported in more than a hundred 

 letters. In most cases the fish that had been observed were gold-fish, 

 which during confinement in aquariums had learned not to flee before 

 their accustomed attendants. The same, however, is reported con- 

 cerning trout and other varieties of fish, even selachians. In many 

 instances fish became so tame that they allowed themselves to be seized 

 by persons they knew, taken out of the water, and replaced in the 

 aquarium. By an observer in the Laboratoire de Zoologie et de Physi- 

 ologic Maritime du College de France, at Concarneau, I am informed 

 that a dog-shark {Scyllkmi catulus) not only swims up to the attendant 

 who brings food and permits the latter to stroke him, but occasionally, 

 on catching sight of the attendant, he works himself up with his tail and 

 his fins in an angle of the glass panes of the aquarium, so that his head 

 protrudes above the surface of the water. The same was noticed in a 

 conger eel in the Laboratoire. Von Mushage, in Sablon-Montigny, 

 reports that a mud-fish ( CohltisfossiUs) wdiich he had repeatedly caught 

 when cleaning the aquarium now slips into his hand of its own accord 

 and lies there curled up. Walther tells of a trout which, on first 

 being put into the aquarium, was in the habit of jumping up out of the 

 water whenever the door was opened; later it ceased to do so. From 

 Takkamen, Siam, S. S. Flower writes that a shoal of Trlcho(/aHet\ 

 extremely shy when first confined in the aciuarium, later on came read- 

 ily to be fed, and certain individuals submitted quietly to being taken 

 out of the water. For years a gold-fish was \x\ the habit of coming up 

 to a setter dog and playing with his tongue, and even tried to do it 

 through the glass panes of the aquarium (H. MuUert, New York). 



This tameness usually loses itself if conditions undergo an essential 

 change — usually, not always. For instance, a trout that had. been 

 removed from a pond to a little fish globe, and had long been fed there, on 

 being returned to the pond continued to feed from the hand. As a rule, 

 however, fish resume their timid ways with a change in the conditions 



SM yy 25 



