234 THE ZOOLOGIST. 



sustenance of the more predaceous kinds. He should endeavour 

 to collect reliable information respecting the plants and animals 

 which afford them sustenance and shelter, as well as ascertain 

 what are their enemies or their friends, and what conditions 

 favour the presence or absence of either class. Irrespective of 

 the foregoing, he should consider the relationship of temperature, 

 currents, soils, and the various conditions of the water in which 

 they reside, to their migrations, growth, health, and reproduction. 

 He should also ascertain whether fish are increasing in numbers, 

 decreasing, or if the supply remains unchanged ; if the size of 

 those captured is augmenting or lessening ; if their condition is 

 better or worse than it was. Should investigations lead him to 

 conclude that fisheries are being unduly depleted, he should care- 

 fully note in what families of fish such is occurring, if possible 

 the cause ; while in marine forms it is likewise necessary to inquire 

 if fishermen have to go further out to sea to obtain their captures, 

 if the killing powers of their implements have inci-eased, and 

 whether more men are now required to obtain the same amount 

 of fish than was the case a few years previously. Lastly, it may 

 be observed that, unless the investigator is able to distinguish the 

 various species, he may easily imagine that he sees in some small 

 forms, as the Solenette [Solea mhmta), the young of the more 

 valuable kinds as the Common Sole [S. vulgaris), whereas he is 

 merely examining one sort that is worthless, except as food for 

 the larger kinds. 



Our fresh-water fishes are divisible into the river or "fluviatile" 

 and the " lacustrine " or lake forms, while our marine ones may 

 be considered as shore or " littoral " and " pelagic" or sea-species ; 

 these last being again subdivided into such as are generally found 

 near the surface, at greater or mid-depths, and abyssal residents, 

 or such as live in the deep sea, below the limits to which the sun's 

 rays penetrate. 



Fresh-water fishes may be permanent residents therein, as 

 Carps ; " anadromous," or merely visitants from the ocean for the 

 purpose of depositing their spawn, and generally, but not in- 

 variably, leaving their young to be reared there, as the Salmon ; 

 " catadromous," or such as reside in fresh waters, visiting the 

 littoral zone or sea in order to breed, as Eels, the young of which 

 ascend into and are reared in our rivers. 



To meet the destructive agencies to which the eggs and young 



