324 FISHES AND FISHING 



ficial 100 or 50 fathoms of the ocean provide valuable 

 records, but the lack of any net at once capable of 

 capturing any but the youngest and smallest fishes, 

 and of being opened and closed at ascertainable depths, 

 leaves us practically in absolute ignorance of the in- 

 habitants of the middle depths of the ocean. Series of 

 hauls taken at the same spot with similar nets fished 

 open from different depths, may afford some evidence 

 of the horizon at which a species is most abundant. 



Some slight evidence on this subject has been derived 

 from closing tow nets ; but a tow net is ill adapted 

 for the capture of adult fishes, and it is most unsafe to 

 assume that such adults are to be found at the same 

 horizon as the larval and young forms of the species 

 to which they belong. 



We believe that for the capture of such larval and 

 young fishes as live in the upper waters of the ocean, a 

 tow net should be allowed to sink to about 100 fathoms, 

 since existing records rather point to the region lying 

 between 100 and 25 fathoms as the normal habitat of 

 such forms, which are comparatively scarce at the 

 actual surface. Interesting results could probably be 

 obtained by the use of tow nets opening and closing at 

 different depths within this region fished by night. 



Wherever possible, a temperature record, taken at 

 the depth at which the gear was supposed to be 

 working, should accompany observations made in the 

 open ocean. 



Preservation of Specimens. 



Two preservatives are ordinarily employed in the 

 case of fishes : (i) alcohol, in some form or other ; and 

 (2) formalin. 



Alcohol has the disadvantage of having to be carried 

 about, of a strength nearly that at which it is used ; it 



