300 FOUNDERS OF OCEANOGRAPHY 



hatchery, do something to repair the damage and avert or 

 delay the destruction of a local fishery. 



It may be pointed out further that, even though the young 

 fish, such as plaice, are turned out to sea soon after being 

 hatched, say about the time of the absorption of the food- 

 yolk, they have been protected from their natural enemies 

 during some three or four weeks at least — about half the 

 time from the egg to the metamorphosis — and that, moreover, 

 is the period when, as eggs, embryos, and young larvae, they 

 are most feeble and defenceless and most in need of artificial 

 protection (see Plate XXVIII). 



We find at the Port Erin hatchery that, although the 

 periods of embryonic and larval life vary to some extent — 

 probably with the temperature of the sea-water — the average 

 times are as follows, in the case of the plaice : — • 



Embryo, from fertilization of egg to hatching, in February, 24 days. 



„ „ „ „ „ in March, 22 days. 



in April, 20 days. 

 Larva, from hatching to absorption of yolk, about 7 or 8 days. 

 Post-larval, absorption of yolk to metamorphosis, 28 to 40, say 



34 days. 



The most significant work, and interesting experiments 

 in connection with artificial operations, have been carried 

 out by the United States Bureau of Fisheries and by the 

 Fishery Board for Scotland. One example may be given 

 from the work of each of these organizations. It has been 

 long recognized that if a species of fish could be introduced 

 into an area where it was previously unknown, that would 

 be satisfactory evidence of the success of artificial operations, 

 and the United States Bureau has shown in its successive 

 Annual Reports of the Commissioner of Fisheries that by 

 collecting and hatching the eggs of the shad {Clupea sapidis- 

 sima) on the Atlantic coast and setting the larvae free in 

 the Pacific in the neighbourhood of the Sacramento river, 

 a profitable shad-fishery has been estabhshed on the 

 Californian coast. The last report published shows that 



