46* REPORT OF COMMISSIONER OF FISH AKD FISHERIES. 



prosecution of the work of hatching various species of fish it will be very 

 desirable to have careful exiieriments instituted beforehand on this sub- 

 ject. It is well known that the eggs of the shad, trout, and salmon are 

 heavier than fresh water, as their tendency is to sink to the bottom of 

 the vessels in which they are kept. Their specific gravity is probably 

 quite constant in the same species, although possibly differing somewhat 

 in the different stages of development. 



Mr. Milner has furnished a memorandum to the effect that in five lots 

 of eggs of the California salmon, tested on the 29th of January, 1878, 

 and some of them well impregnated, the specific gravity varied from 1.07 

 to 1.09, two samples giving the first figure and three the second. He 

 found that in brook trout treated on the same day, among which a few 

 were hatching prematurely, the density of the two lots varied from 1.156 

 to 1.159, showing a very appreciably greater density in the latter. I 

 would commend to persons who have facilities for making similar inves- 

 tigations, to determine the difference between the density of the unim- 

 l)regnated egg, the freshly impregnated egg, and the same series of eggs 

 at different stages of growth, including that of the recently hatched 

 embryo. 



The European Turbot and Sole (Bliomhus maorvmus and Solea vulgaris). 



It is a well-established fact tljftt the United States, in the abundance 

 and vaiiety of first-class food-fishes is greatly in advance of any single 

 country in Europe, even of Great Britain, since, while i^ossessing the 

 various species of the cod family, the halibut, mackerel, herring, &c., in 

 common with them, America can show the Spanish mackerel, the pom- 

 pano, the channel bass, the weak-fish, and many other species of eatable 

 qualities. Any assertion of this superiority on the part of the United 

 States is met by the assurance that in the lack of the turbot and sole, 

 America is without the two finest of all species. There is no question 

 as to the excellence of these fish, especially of the sole, although in the 

 new Pole or Craig flounder, a deep-sea fish discovered by the United 

 States Fish Commission in such enormous abundance off the coast of 

 Massachusetts in 1877, we have what vnll measurably replace the 

 turbot ; and several of our species of flat fish are scarcely, if at all, in- 

 ferior to the sole. 



The importance of having these two European species in our own 

 waters has, however, been suggested to the United States Fish Com- 

 mission, and it was concluded to take such steps as might be possible to 

 obtain them. Among the gentlemen particularly interested in this 

 transfer was Mr. J. G. Kidder, of Boston, who kindly offered his services 

 with the Cunard Steamship Line from Boston to secure free passage for 

 the fish and their attendant from Liverpool to Boston. He accordingly 

 obtained letters from the agent of the line, at Boston to the directors in 

 Liverpool which accomj)lished their desired object. 



Eeference has already been made to the agency of Mr. Fred IMather 



