386 Professor W. C. Mcintosh [Feb. 1, 



Anstrutlier. In the sea, however, they are seldom met with on the 

 surface, and the tow-nets require to be snnk a fathom or two to 

 capture them, for their specific gravity is so little less than that of 

 sea water that they are carried hither and thither by the currents in 

 everv direction. Some indeed are captured near the bottom by nets 

 attached to the trawl-beam, while experience with the large net of 

 the St. Andrews Laboratory has proved that a great number are 

 carried in mid water. 



When these glassy eggs issue from the female fish they are soon 

 fertilised in the surrounding water : so that in British seas at any 

 rate non-fertiKsation is one of the rarest conditions in pelagic 

 ecrcrs. It is indeed more likely to happen in the case of the herring, 

 which deposits its eggs in masses on the bottom, or in artificial 

 circumstances in tanks. The unfertilised egg soon becomes opaque 

 and sinks, so that it is readily recognised. 



In this connection I would again refer to the notion not long ago 

 firmly rooted in the minds of many — especially those practically 

 engaged in fishing — that the fishes at the spawning season seek the 

 shallow water in which to deposit their eggs. Now there is little 

 in nature to support this idea. Shore-fishes it is true, such as the 

 lump-sucker and sea-scorpion (Cottus scorpius), do deposit their eggs 

 there (and there cannot be a doubt that some of the masses of eggs 

 thus deposited have been mistaken for those of the f(X)d-fishes), but 

 the edible fishes proper, such as the cod, haddock, whiting, flounders, 

 and others, appear to produce their eggs just where they happen to 

 be feeding at the season. Their eggs are taken in charge by the 

 ocean generally, and hence are independent of any imaginary protec- 

 tion or privilege pertaining to the shallow waters. 



Moreover, it does not follow that the fishes of an enclosed bay * 

 will increase of themselves. As in the case of the plaice, in shallow 

 sandy bays, it may happen that most of the large mature fishes are 

 beyond the limits, the half-grown or immature forms mainly occur- 

 ring within : pelagic ova therefore must be borne inward, and still 

 more the pelagic young, while the post-larval stages likewise migrate 

 sborewards ; a counter-migration of the older forms subsequently 

 taking place to the deeper water. Such biys therefore, have to 

 depend for their stock of fishes on the unprotected off'shore. If by 

 any chance the latter waters were depopulated the inshore would 

 seriously sufier.t 



The minute size of the eggs of all the important marine food- 

 fishes enables a fish like the codL for instance, to produce an enormous 

 number— probably about 9,000,000 as against the 18-25.000 of the 

 salmon, or the 10^30,000 of the herring, both of which fishes deposit 



* For example, closed bv a Fi=h.ery Order. 



T This ffetare was x>ointed out in the ' Report of H,M. Trawling CommisiioD, 

 nnder Lord Dalhousie.' 



