380 HAVE FISHES MEMORY. 



that in the main they lacked nerves. Such a thing as learning the 

 swimming motion is not a probable conjecture, in spite of the appar- 

 ent necessity among higher animals to make an etiort to acquire the 

 motion of walking, flying, etc. A great part of this efl'ort is found to 

 be nothing more than a strengthening of the innnature muscular sys- 

 tem. Microscopic examination of the anatomy of the spinal cord 

 reveals that all the fibers and cells necessary to put into motion the 

 organs of walking exist long before a human being learns how to use 

 his limbs. At all events, the most exhaustive study of the spinal cord 

 fails to indicate that any essential change sets in after the first year 

 of life. 



Inquiries into the sense impressions of fishes are not numerous, and 

 as most of them have been conducted by la^'men, they, as a rule, take 

 no account of pu})lished results. In fact, the literature on the subject 

 has nowhere been collected in proper form. Doubtless some works 

 have, therefore, escaped my attention. The best I am acquainted with 

 is that b}'^ Bateson, on the conduct of fishes with reference to sense 

 irritations that act upon them under the normal conditions of their life. 

 Bateson^ studied very many species of fishes, especially in their rela- 

 tion to food and breeding, at the marine aquarium at Plymouth. 



As for the response to chemical irritations by the two senses of smell 

 and taste, which in a(|uutic animals can not be distinguished from 

 each other, it appears that the discriminating faculty is slight. The 

 conger-eel ate meat smeared with spirits of iodoform, trimcthylamine, 

 spirits of camphor, and extract of anchovies. It refused, however, to 

 touch cooked meat or meat treated with acids, due perhaps to the 

 sense of touch residing in the organs of the mouth. Other fishes that 

 have been observed act similarly. Smells did not disturb them; they 

 were oblivious of stones smeared with the above substances; they 

 paid no attention even to putrefying roe — it was the spawn of another 

 family of fishes. A number of fishes, however, of which the flat- 

 fishes (flounders, etc.), are a type, find their food chiefly by means 

 of chemical sense impressions. They may be lying quiet when the 

 food or the juice of food is introduced into the aquarium. When the 

 odor issuing from it spreads, they grow restive and seek until they 

 find the food, or, in case only the juice was dropped in, until they 

 finally grow weary. Motella tricirrata fails to see worms moving quite 

 close to it, but as soon as it scents them it moves to and fro restlessly 

 until it happens across them. If the organ of smell was removed 

 from this fish, it could not find its food, although its barbels and its 

 eyes were perfect. 



In no instance has an animal of this type, though equipped with 

 sight, recognized food through vision. 



1 W. Bateson, The Sense Organs and Perceptions of Fishes, with Remarks on the 

 Supply of Bait. (Journal of the Marine Biological Association of the United King- 

 dom. Vol. 1, 1889-90, p. 225.) 



