ii8 



III. 



Have Fish a Memory? 



A CHAPTER IN THE EVOLUTION OF THE BRAIN. 



FEW contrasts are more striking than that between the nebulous 

 metaphysical psychology of former generations and the modern 

 development of that science on physiological lines. It would now 

 appear that comparative anatomy is likely to prove of inestimable 

 value in its further advance ; and for this, science is largely indebted 

 to Professor Ludwig Edinger of Frankfurt, whose labours in this 

 field, extending now over many years, have already gone far to 

 establish a veritable science of comparative psychology. Professor 

 Edinger asks us to publish an appeal for information on the subject of 

 the existence of memory in fishes. The importance of this question, 

 perhaps at first sight not very apparent, is clearly shown in the light 

 of an address which he has published in the Allgemeim Medicinische 

 Central Zeitung for 1896 (Nos. 79 and 80) on the Development of the 

 Brain-tracts in the Animal Series, which lies before us, and a short 

 account of which will not only prove of interest to our readers, but 

 may help to stimulate a response to the question propounded by its 

 author. 



His contention is briefly this. No hard and fast line exists 

 between the mental capacities of the lowest and highest vertebrates. 

 We ought to be able to trace the various transitional stages, and by 

 the Hght of comparative anatomy and histology to assign their true 

 psychological value to the different nervous structures which make 

 their appearance in ascending the animal scale. But to do this we 

 require much new and detailed information as to the mental capacities 

 of various groups of animals ; and in collecting this it must not be 

 taken for granted that apparently deliberate and purposeful actions 

 are in reality due to conscious volition as we understand it in the 

 higher animals. Professor Edinger denies that in lower organisms 

 the lower nerve-centres, which alone are present, can fulfil the same 

 functions as the higher centres, which are first to be found higher up 

 in the animal scale. He regards the appearances of conscious volition 

 shown by such invertebrates as a sea-anemone or an earthworm as 

 purely reflex : it is the observer who is apt to employ too " anthropo- 

 psychic " a standard in their interpretation. It has been demonstrated 

 by Retzius that the ventral nerve-cord of an earthworm contains a 

 complete and elaborate reflex mechanism : — afferent sensory fibres 

 which, after sub-division, are connected with the dendritic processes of 



