ARTIFICIAL HATCHING OF FISH. 101 



stood; the spawning-bed being made, not by the 

 ploughing of the fish's nose, as is generally stated, 

 but, according to Mr. Shaw, by the action of the 

 tail, and solely by the female, throwing herself at in- 

 tervals* of a few minutes upon her side ; and while 

 in this position, by the rapid movement of her tail, 

 digging a receptacle in the gravel for her ova, a por- 

 tion of which she deposits ; and again turning on 

 her side, covering them up by the renewed action of 

 her tail, — thus alternately digging, depositing, and 

 covering the ova till the process is completed, which 

 is usually in three or four days. (Edin. Phil. Trans, 

 xiv. 565). — The subject of Artifical Hatching also 

 has been much elucidated by the labours of Mr. 

 Shaw, Professor Agassiz, Sir Francis M'Kenzie, 

 and others, an object of importance chiefly in rela- 

 tion to the more valuable kinds of fresh-water 

 fish. How long the ova may remain extruded 

 from the body of the female and continue suscep- 

 tible of the fecundating influence of the milt, has 

 not hitherto been ascertained. Mr. Shaw states 

 that in one instance the female had been dead for 

 nearly two hours without the vital principle being 

 in the slightest degree affected, thus corroborating 

 M. Jacobi's experiments on this point. Nothing 

 can be simpler than collecting the Spawn which has 

 been recently impregnated ; or than artificially im- 

 pregnating it, by securing the parent fishes, when 

 engaged in the process, confining them in some 

 natural or artificial receptacle, and then disposing of 

 it as we wish. If left in its native bed, immense 



