CHAP. v. Fish Communicate Ideas. 85 



ear. It is equally comprehensible that, as in the case of ants and 

 animals, they may be made by distinct means, means of which we have 

 no knowledge. 



It has been remarked above that it is difficult to conceive how any 

 creatures who habitually live in collected numbers could possibly order 

 their conduct so as to live harmoniously, unless they had the power of 

 freely interchanging their ideas. May not such a remark have equal 

 pertinence to fish as to birds ? Is it not equally applicable to such fish 

 as swim in shoals? Porpoises, for instance, act very obviously all in 

 concert, and the change, from one unity of purpose to another unity or" 

 purpose, is made with such rapidity, and such a complete embracing 

 of every individual of the school, that it is easier to believe that the 

 new idea was in some way communicated, than to believe that it was 

 not. Gregarious fish, such as the herring and the pilchard, could 

 scarcely conduct their migrations in unison if they had not all a 

 common intent arrived at by communication. The simultaneous 

 manner in which a vast shoal of fish will descend from the surface of 

 the sea to deeper water points also in the same direction. It is well 

 known to anglers that you may catch dace after dace out of a shoal till 

 you have hooked and lost one in the landing, and that then you will 

 ordinarily get no more dace out of that shoal. How is this to be 

 accounted for except on the supposition that they have powers of 

 communication analogous to those of gregarious animals on land? 

 Exceptional days there are certainly, that come once or twice in a 

 twelvemonth, when nothing will dissuade the dace from taking as fast 

 as you can throw in your fly. But those exceptions militate not against 

 the general rule, and the conclusion I have drawn ; they only indicate, 

 as in an instance above, that on those exceptional days appetite over- 

 masters prudence, despite communicated cautions. The male stickleback 

 is known to build a nest, and then to find and bring a female partner to 

 it. Why should it not be believed that the male stickleback made a 

 communication that induced the female to accompany him, just as 

 much as such communications are believed to be made by dogs and 

 other animals which live on the land ? The fact of living wholly on 

 the land, or much in the air, or wholly in the water, does not seem to 

 affect the question. It affects only our facilities for observation by 

 limiting them sadly. But, as far as observations go, they seem to 

 indicate that there is no difference in this respect between fish and 



