114 INTRODUCTION. 



probably been long and practically known. (Zool. 

 Jour. ix. 32). 



As much as our limits permit, has now been said 

 upon this interesting topic, and enough, we trust, to 

 excite renewed attention to it. Probably different 

 fish are very differently constituted as to their sus- 

 ceptibility of such a change of habit. To some, we 

 believe, the immediate removal from salt-water to 

 fresh, is instant death ; but it ought not to be for- 

 gotten, that the majority of those which voluntarily 

 cbange their residence from sea-water to fresh, 

 generally linger for a while on the confines ere they 

 make a decided move. Upon the whole, however, 

 this matter appears to be more interesting in a 

 physiological than in a practical point of view, in- 

 asmuch as it should be kept in mind that there 

 exists no difficulty in forming, near the sea, sea- 

 water ponds, or Vivaria, as well as fresh ; and that 

 fish may thus be easily accommodated, according to 

 their necessities and tastes. 



The subject of Vivaria or Preserves, and their 

 proper Stocking and Management, opens up an im- 

 portant branch of the subject Avhich has been too 

 much neglected. Mr. Boccius' little Essay is use- 

 ful on the point of Fresh-water Preserves. He re- 

 commends three ponds to be in connexion with each 

 other, respectively of three, four, and five acres, and 

 shows how a lucrative rental may be derived from 

 them ; stocking the first with 600 Carp, 60 Tencli, 

 and 60 pikes. On Tench, he tells us, no fish will 



