378 HAVE FISHES MEMOEY. 



"Therefore it is extremely important that all pertinent o])servation.s 

 should be gathered together again and elaborated anew. 



"The undersigned requests all in a position to observe tish, espe^ 

 cially anglers and fishbreeders, to be good enough to send him data 

 bearing upon the subject. In particular, he would beg that facts long 

 accepted as such, if their correctness has been tested by recent observa- 

 tions, be communicated to him." 



This appeal was attended bj' most satisfactory results. Within a few 

 months I received an abundant crop of communications from all parts — 

 from Germany, England. France. North America. Siam. India. It was 

 surprising to note the interest of breeders, anglers, students of nature, 

 and dilettanti. Equall}^ surprising and delightful was the circumstance 

 that comparativeh' few of the connnunications proved wholly worth- 

 less. The majority' of ni}" correspondents knew how to observe and 

 report with unassailable accuracy. Two-thirds of the two hundred 

 letters available were written in German, one-third in English. Only 

 one French correspondent addressed me. The appeal w^as composed 

 with a view to eliciting as much material as possible relative to the 

 "intelligence," etc., of fishes. The motives for the investigation were 

 not laid bare in their entirety, and the wording was made as simple as 

 possible. The happy result w^as that numerous letters, many of them 

 among the best that came, were received from persons like fishermen, 

 attendants in aquariums, etc., whose occupations bring them close to 

 fish. A gendarme, for instance, was moved to institute an investiga- 

 tion of his own among a number of fishermen, etc., and he sent me his 

 results detailed with clearness and precision. I take this opportunit}'^ 

 to express m}^ thanks to all my correspondents. 



The brain of osseous fishes is pretty accurately known. The nerves 

 of sense, like those in the higher animals, lose themselves in their 

 primary termini, but not the faintest path can be traced from these 

 to anything resembling cortical substance. There is absolutel}^ no 

 cortex. These animals, then, must confine their activity to the primary 

 termini. Accordingly, the ganglia are very much more developed 

 than the corresponding ones in the mammalia. They do not, to be 

 sure, differ essentially in composition from the ganglia of other ani- 

 mals, but what there is of them is developed more robustly. The 

 fibers that appear only sparingly in the mammals, the ganglia which 

 in the higher animals are only rudimentary, are strongly in evidence 

 in fishes, and lend themselves readily to examination. 



If, now% we wish to find out the functions of this apparatus, we 

 must begin by determining the sense impressions fishes can receive. 

 Do they see, or hear, or feel? Are they, perhaps, in possession of 

 sense qualities lacking in other animals? 



The reply to these preliminary questions must be our first task. 



Whether a stimulus takes effect or not can be inferred only from 

 the movements following upon its application. In the first steps of 



