INTRODUCTION. xxi 



Even their sight in the depths which they frequent could have little exercise, if most 

 of them had not, in the size of their eyes, a means of compensation for the feebleness of 

 the light ; but even in these the eye hardly changes its direction, still less by altering its 

 dimensions can it accommodate itself to the distances of objects. The iris never dilates or 

 contracts, and the pupil remains the same in all intensities of illumination. No tear ever 

 waters the eye — no eyelid wipes or protects it — it is in the fish but a feeble representative 

 of this organ, so beautiful, so lively, and so animated in the higher classes of animals. 



Being only able to support itself by pursuing a prey, which itself swims more or less 

 rapidly, having no means of seizing it but by swallowing, a delicate perception of savours 

 would have been useless if nature had bestowed it ; but their tongue, almost motionless, often 

 entirely bony or coated with dental plates, and only furnished with slender nerves, and these 

 few in number, shows us that this organ also is as obtuse as its little use would lead us to 

 imagine. Their smell even cannot be exercised so continually as in animals which respire 

 air and have their nostrils constantly traversed by odorous vapours. 



Lastly, their touch, almost annihilated at the surface of their body by the scales which 

 clothe them, and in their limbs by the want of flexibility in their rays, and the nature of the 

 membranes investing them, is confined to the ends of their lips, and even these in some are 

 osseous and insensible. 



Thus, the external senses of fishes give them few lively and distinct impressions. Sur- 

 rounding nature cannot affect them, but in a confused manner ; their pleasures are little varied, 

 and they have no painful impressions from without but such as are produced by wounds. 



Their continual need, which, except in the breeding season, alone occupies and guides 

 them, is to assuage the internal feeling of hunger, to devour almost all that they can. To 

 pursue a prey or to escape from a pursuer makes the occupation of their life ; it is this which 

 determines their choice of the different situations which they inhabit ; it is the principal cause 

 of the variety of their forms, and of the special instincts or artifices which nature has granted 

 to some of the species. 



Vicissitudes of temperature affect them little, not only because these are less in the 

 element which they inhabit than in our atmosphere, but because their bodies taking the sur- 

 rounding temperature, the contrast of external cold and .internal heat scarcely exists in their 

 case.* Thus the seasons are not so exclusively the regulators of their migration and propa- 

 gation as amongst quadrupeds, or more especially birds. Many fishes spawn in winter; it is 

 towards autumn that Herrings come out of the north to shed upon our coast their spawn and 

 milt. It is in the north that the most astonishing fecundity is witnessed, if not in variety of 

 species, at least in individuals ; and in no other seas do we find anything approaching to 

 the countless myriads of Herrings and Cod which attract whole fleets to the northern fisheries. 



The loves of fishes are cold as themselves ; they only indicate individual need. Scarcely 

 is it permitted to a few species that the two sexes should pair, and enjoy pleasure together ; 

 in the rest the males pursue the eggs rather than seek the females ; they are reduced to 

 impregnate eggs, the mother of which is unknown, and whose produce they will never see. 

 The pleasures of maternity are equally unknown to most species ; a small number only carry 

 their eggs with them for a short time; with few exceptions fishes have no nest to build and 

 no young to nourish ; in a word, even to the last details, their economy contrasts diametrically 

 with that of birds." t 



* Sudden change of temperature, however, does affect some kinds of fish in a most marked manner. When 

 placed at once into very cold water, at a temperature considerably lower than the water from which they have been 

 taken, fish will often turn on their backs, become apparently paral3'zed and die. The reader will find some interesting- 

 experiments on "The Degree of Temperature fatal to Fishes," — the temperature in these cases being that of warm or 

 hot water — in Dr. J. Davy's Physiological Researches, p. 297-305. The experiments were made at Oxford some years ago 

 in conjunction with Mr. Robertson, Demonstrator at the Museum, Oxford, and my valued friend, Professor Rolleston. 



t Cyclop. Anal. Sf Phys., iii. p. 955-6. 



