1884.] HYBRIDS AMONG THE SALMONID.E. 27 



1875, and placed in the island-pond in 1879, when it was finally 

 completed. This pond is 210 X 90 feet, and from 10 to 11 feet deep 

 in the centre. 



One can hardly assert that the fish thus kept have been under the 

 same conditions of existence as if they had been in a wild state in 

 Scottish waters. Always provided with food, they may have thus 

 been somewhat stimulated, and their powers of propagating their 

 species accelerated. This may tend to shorten life, as sterility in 

 fishes appears to lengthen it. It has been apparent that males ex- 

 perience a larger mortality than females, due apparently to exhaustion 

 after breeding, which seems to be assisted by their pugnacious pro- 

 pensities. 



I last year remarked upon the fact observed at Hovvietoun, that, 

 as a rule, the Lochleven variety of Trout gave eggs of different 

 sizes in accordance with the age of the parents. Those which were 

 hatched in 1876, or six years old, were producing ova 32 of which 

 filled the length of a glass quill, whereas those which were hatched 

 in 1875, or seven years old, gave ova 27 or 28 of which occupied the 

 same space. 



Since then I have come across several interesting statements, 

 which fully bear out the observations made at Howietouu. In the 

 Report of the United-States Fish Commission on the McCloud 

 River, for 1878, it is observed that " the parent Salmon were un- 

 usually small, their average weight being under eight pounds. This 

 small size was stated to be undoubtedly caused in whole or in part 

 by the fishing at the canneries of the Sacramento, where the 8-inch 

 meshes of the innumerable drift-nets stopped all the large Salmon 

 but let all the small ones through. The eggs when taken proved to 

 be at least a third smaller than those of most previous years, and the 

 average number of eggs to the fish was about 3500 against 4200 

 in the previous year." In this case the diminished size of the 

 parents may have not only conduced to diminished size of the ova, 

 but likewise to a decreased amount, for the number generally is pro- 

 portionate to the weight of the parent fish. 



Livingston Stone adduces another reason for this result, namely, 

 that American Trout, Salmo fontinalis, living in spring water (which 

 means deficient food) develop smaller ova than such as reside 

 in brook water. That is, poverty in food has the same effect in dimi- 

 nishing the size of the eggs as if the parent had not yet arrived at 

 full sexual maturity. 



I adduce these instances because assertion has been so confidently 

 made to the contrary, and it is perhaps as well to be able to bring 

 forward facts observed at different places by different observers who 

 are not acquainted with the views of one another. Malmgren having 

 observed that the ova of Trutta relicta are considerably smaller than 

 those of the Salmon, Dr. Gunther remarked in the 'Zoological Record' 

 (1864, pp. 180, 181) as follows: — "Thirdly, as Hr. Malmgren ob- 

 serves, in the size of the ova. The last character will be considered 

 very significant by all who may have a more extensive knowledge of 

 fishes, as the size of the ova is not only invariably the same in 



