144 THE CANADIAN NATURALIST. [April. 



The greatest care must be taken to prevent the entrance of in- 

 sects and larvae into the hatching-apparatus. The most dangerous 

 enemy to the ova and the young fish, is, perhaps, the water-newt 

 (^Sorex fodiens) . If the apparatus cannot be raised to a sufficient 

 height above the ground, it should be protected with a perforated 

 tin or zinc lid. 



A curious instance occurred at the hatching-establishment at 

 Greffsen, a water-cure establishment near Christiania, a few years 

 ago. The apparatus was raised two feet above the ground, and 

 was not, therefore, protected with such a lid. A large quantity of 

 eo-ffs had been hatched out, when, one fine mornins::, the 

 young fry had nearly all disappeared! A number of traps 

 were accordingly set on the floor of the house, and the following 

 morning the intruder was captured. It turned out to be a water- 

 rail, which had found ingress through the mouth of the drain. 



The Dytisci, HydropMli, and their larvae, and the larvae of the 

 Libellula and Agrion, are also very dangerous enemies. The 

 Libellula depressa is especially a deadly foe, and will even devour 

 the fish of two to three months old. It is extremely tenacious of 

 life ; and has been known, after having been kept a whole day in 

 spirits, to recover when placed in water where there were young 

 fish, and in a very short time to commence attacking them as if 

 nothing had happened. 



Proved Facts in the History op the Salmon : By 



H. C. Pennell. 



1. Salmon and Grilse invariably spawn in fresh water if pos- 

 sible ; both the eggs, and the young fry whilst in the Parr state,, 

 being destroyed by contact with salt water. 



2. The eggs are usually deposited on gravelly shallows, where 

 they hatch in from 80 to 140 days, according to the temperature 

 of the water. Eggs remaining unhatched beyond the latter period 

 will seldom hatch at all, possibly from having been destroyed by 

 the low temperature. 



3 The eggs deposited by the female will not hatch under any 

 circumstances unless vivified, after exclusion, by the milt of the 

 male ; and — at least up to the period of migration — there is no 

 difference whatever in fry bred between Salmon only, between 

 Grilse only, between Salmon and Grilse, between Salmon and 

 Parr, or between Grilse and Parr. 



