OF FISHES IN GENERAL. 



247 



But the truth is, the fish can neither in- 

 crease nor diminish the quantity of air in its 

 air-bladder at will, no more than we can that 

 which is contained in our stomachs. The 

 animal has no one muscle, much less a pair of 

 muscles, for contracting or dilating this or- 

 gan ; its aperture is from the gullet ; and 

 what air is put into it must remain there till 

 the necessities, and not the will of the animal 

 call it forth as a supply. 



But, to put the matter past a doubt, many 

 fish are furnished with an air-bladder, that 

 continually crawl at the bottom ; such as the 

 eel and the flounder ; and many more are en- 

 tirely without any bladder, that swim at ease 

 in every depth ; such as the anchovy and 

 fresh-water gudgeon. 1 Indeed, the number 

 of fish that want this organ is alone a suffi- 

 cient proof that it is not so necessary for the 

 purposes of swimming; and as the ventral 

 fins, which in all fish lie flat upon the water, 

 seem fully sufficient to keep them at all 

 depths, I see no great occasion for this inter- 

 nal philosophical apparatus for raising and de- 

 pressing them. Upon the whole, the air- 

 bladder seems adapted for different purposes 

 than that of keeping the fish at different depths 

 in the water ; but whether it be to supply them 

 with air when it is wanted from without, 

 or for what other purpose, I will not take 

 upon me to determine. 



Hitherto we have seen fish in every res- 

 pect inferior to land animals ; in the simpli- 

 city of their conformation, in their senses, and 

 their enjoyments ; but of that humble exis- 

 tence which they have been granted by na- 

 ture, they have a longer term than any other 

 class of animated nature. " Most of the dis- 

 orders incident to mankind," says Bacon, 

 ** arise from the changes and alterations of the 

 atmosphere ; but fishes reside in an element 

 little subject to change ; theirs is a uniform 

 existence ; their movements are without ef- 

 fort, and their life without labour. Their 

 bones also, which are united by cartilages, 

 admit of indefinite extension ; and the differ- 

 ent sizes of animals of the same kind, among 

 fishes, is very various. They still keep grow- 

 ing ; their bodies, instead of suffering the 

 rigidity of age, which is the cause of natural 

 decay in land animals, still continue increas- 

 ing with fresh supplies ; and as the body 

 grows, the conduits of life furnish their stores 

 in greater abundance. How long a fish, that 

 seems to have scarcely any bounds put to its 

 growth, continues to live, is not ascertained ; 

 perhaps the life of a man would not be long 

 enough to measure that of the smallest." 



There have been two methods devised for 

 determining the age of fishes which are more 



- 



Redi. 



ingenious than certain ; the one is by the cir- 

 cles of the scales, the other by the transverse 

 section of the back-bone. The first method is 

 this : When a fish's scale is examined through 

 a microscope, it will be found to consist of a 

 number of circles, one circle within another, 

 in some measure resembling those which ap- 

 pear upon the transverse section of a tree, and 

 supposed to offer the same information. For 

 as in trees we can tell their age by the num- 

 ber of their circles, so in fishes we can tell 

 theirs by the number of circles in every scale, 

 reckoning one ring for every year of the ani- 

 mal's existence. By this method, Mr Buffbri 

 found a carp, whose scales he examined, to be 

 not less than a hundred years old ; a thing al- 

 most incredible, had we not several accounts 

 in other authors which tend to confirm the 

 discovery. Gesner brings us an instance of 

 one of the same age ; and Albertus of one 

 more than double that period. 



The age of the skate and the ray, that want 

 scales, may be known by the other method ; 

 which is, by separating the joints of the back- 

 bone, and then minutely observing the num- 

 ber of rings, which the surface where it has 

 joined exhibits. By this the fish's age is said 

 to be known ; and perhaps with as much cer- 

 tainty as in the former instance. 



But how unsatisfactory soever these marks 

 may be, we have no reason to doubt the great 

 age of some fishes. Those that have ponds, 

 often know the oldest by their superior size. 

 But the longevity of these animals is nothing 

 when compared to their fecundity. All sorts, 

 a few of the larger ones excepted, multiply 

 their kind, some by hundreds, and some by 

 millions. There are some that bring forth 

 their young alive, and some that only produce 

 eggs : the former are rather the least fruitful ; 

 yet even these are seen to produce in great 

 abundance. The viviparous blenny, for in- 

 stance, brings forth two or three hundred at 

 a time, all alive, and playing round the pa- 

 rent together. Those who exclude their pro- 

 geny in a more imperfect state, and produce 

 eggs, which they are obliged to leave to 

 chance, either on the bottom, at the edge of 

 the water, or floating on the surface where it 

 is deeper, are all much more prolific ; and 

 seem to proportion their stock to the dan- 

 ger there is of its consumption. Of these 

 eggs thus deposited, scarcely one in a hundred 

 brings forth an animal; they are devoured by 

 all the lesser fry that frequent the shores ; by 

 aquatic birds near the margin ; and by the 

 larger fish in deep water. Still, however, 

 there are enough for supplying the deep with 

 inhabitants ; and, notwithstanding their own 

 rapacity, and that of the fowls of various 

 tribes, the numbers that escape are sufficient 

 to relieve the wants of a very considerable 



