2194 Fishes. 



is as absolutely necessary to life as it is the slow destroyer of all things. The destruc- 

 tion of the eggs of the trout, from the cause just assigned I have proved to many 

 friends, having shown them thousands in a putrefied state on their own natural hills 

 or breeding-grounds ; whilst upon the principles I have to detail of my methods of 

 producing fish, not a single egg is lost." — p. 1 . 



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" Strange to say, however, the very cause of destruction to the fish while in em- 

 bryo produces them abundance of food when once brought into life. For instance, 

 the very mud or alluvial deposit in our rivers and streams, which is an enemy to the 

 embryo, breeds such myriads of worms, larvae and insects, that when the young fish 

 — all dangers overcome — find their way into it at last, they have no labour to procure 

 food, and increase rapidly in size as a consequence of the easy life they lead : for it is 

 a well-authenticated fact, that fish which have to toil hard in hunting for their food 

 are bony and ill-conditioned, and never fat." — p. 6. 



" In proof of the extraordinary growth of fish when confined and regularly fed on 

 food fit for them, I may refer to the two electric eels (Gymnotus e/.ectricus), now exhi- 

 biting at the Polytechnic Institution. These fish were imported six years back, and 

 placed as objects of curiosity in the Adelaide Gallery, in the Strand, and since have 

 become inmates of the above-named Institution. When brought to this country they 

 weighed about one pound each ; but, being confined in a very small space, and fresh 

 warm water daily given to them, agreeable to their natural element, and regularly fed, 

 the largest of these specimens of Gymnoti has grown to the great weight of between 

 forty and fifty pounds, the smaller one to about forty pounds ; and the cause assigned 

 for this difference in weight is, that the one fish was by nature the most powerful of 

 the two, and always claimed the lion's share of food thrown to them ; and it is a fact 

 worth noticing, that the largest fish of the two has the greatest power in giving the 

 electric shock." — p. 7. 



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" Salmon take one hundred days, trout fifty days, and many other fish forty-two 

 days, to come forth from the egg^ provided the water does not change its temperature 

 during the period of breeding : so that it is not impossible to bring varieties of better 

 sorts of fish from distant countries to stock our streams with, and I should say, from 

 what I have myself experienced, with success. The temperature best adapted for 

 spawning ranges from 53° to 56°, and at this warmth I have never found any alteration 

 in the time I have stated, which may be relied upon as correct, and the true time in 

 every case. Should this even temperature vary very much, then the egg, as the water 

 loses its warmth, is sensibly retarded in its incubation. From this change of tempe- 

 rature I have known the egg of the trout to be delayed from fifty to seventy days ; and 

 when the fry have at last made their appearance, they have invariably been poor weak- 

 lings, and puny in precise proportion to the time lost in their retardation in the egg. 

 After a fish of any description has burst its bounds into life, the vesicle or investing 

 membrane, which encompassed it in embryo, still adheres to the umbilical region, and 

 contains a small proportion of the fluid necessary to the sustenance of the then unpro- 

 tected animal. This vesicle or sack is exhausted of its fluid in fourteen days in trout, 

 and in double that time with srnolts, and then drops off; and by this time Nature has 

 taught these little creatures to hunt for their food, and to avoid danger, which they do 

 by keeping close to the shallows. Carp and tench spawn in June, at the time when 



