76 MR. HOGG ON THE MODES OF 



conjectured that the ova might be conveyed by birds, sticking to 

 their feet. Is it not likely that the voracity of birds may aid in 

 the diffusion of fish ? Is it not probable that some of the ova 

 swallowed by a Water-ouzel or Heron, may be disgorged or dis- 

 charged by the vent, without losing their vitality ?" 



" Piscator " answers : " The same idea has occurred to me, but 

 an experiment I made was opposed to it. You know how high 

 is the temperature of birds : the stomach of the Water-ouzel is 

 probably above 100° of Fahrenheit. Now, this temperature I 

 have found destructive of the life of the embryo." 



Also, in a paper entitled — " Some Observations on the Ova of 

 the Salmon, in relation to the Distribution of Species," which I 

 heard read still more recently to the Royal Society — viz., on April 

 26 last (1855), Dr. Davy repeated part of the preceding, with 

 regard to the transport of the ova in damp weather, by their 

 accidental adhesion to some animal, as a Heron, &c., and likewise 

 in frosty weather. And the abstract of that paper, as published 

 in No. 12, vol. vii. of the "Proceedings of the Royal Society," 

 page 363, thus sets forth some of the results of Dr. Davy's 

 experiments : — 



" Section 2. That the vitality of the ova was as well preserved 

 in air saturated with moisture, as it would have been had they 

 been in water. 



"3. That the ova may be included in ice without loss of 

 vitality, provided the temperature is not so low as to freeze them. 



" 4. That the ova, and also the fry recently produced, can 

 bear for some time a temperature of about 80° or 82° in water, 

 without materially suffering; but not without loss of life if 

 raised above 84° or 85°. 



"5. That the ova and young fry are speedily killed by a 

 solution of common salt, nearly of the specific gravity of sea- 

 water — viz., 1026; and also by a weaker solution of specific 

 gravity 1016. 



" Finally, in reference to the inquiry regarding the distribution 

 of the species of fishes, he expresses his belief that some of the 

 results may be of useful application, especially those given in 

 the 2nd and 3rd sections; inferring that, as in moist air, the 



