its temperature is considerably below 32°, and the scientist knows that the freezing-point of fresh water itself is considerably lowered by increasing the pressure to which it is subjected. To what extent facts may refute reasoning by analogy in the case of the relation of animals to their environment will perhaps be clear from the following examples. On the south side of the Strait of Belle Isle the cod leave when the temperature of the bottom water, where they are living, rises to and above 10° C., as we observed in 1923, yet off Cape Cod the cod has been taken in quantity by the United States Bureau of Fisheries in water with a temperature as high as 14° C., as we have been informed by Dr. H. B. Bigelow. In 1915 Captain Thor Iversen caught in the Gulf of St. Lawrence cod that were living and spawning in water with a temperature below 0°C. (see Report of Canadian Fisheries Expedition, 1914-1915, p. xxvii, Hjort ; and p. 44, Dannevig), yet Adolph Nielsen in his work for the Newfoundland Government (Annual Report of the Newfoundland Fisheries Commission for the year 1893, Appendix No. 1, Report for the Year 1893, by A. Nielsen, Superintendent of Fisheries) found that the cod that he was attempting to hold for spawning purposes were killed when the temperature fell below 0° C. The apparent discrepancies in these facts are doubtless to be attributed not to any errors in observation, but to our use of the word “ cod ” not for one thing, but for a group. The cod species, Gadus callarias, as scientifically defined, certainly includes a very considerable number of varieties or races, differing in geographical distribution, in habits, in temperature relations, and in salinity relations. Such races have been studied in considerable detail in the case of the herring, but we have as yet very little knowledge of those of the cod.
Mobius and Heincke on page 233 of their account of the fishes of the Baltic ( “ Die Fische der Ostsee,” IVte Bericht Comm. Wiss. Untersuchung der deutsehen Meere, s. 193-296, 1883) do indeed separate the cod of the Baltic as a distinct variety, “ Küstendorsch,” from the cod of the North Sea, “ Hochseedorsch,” and they refer to the fact that von Linnée considered the cod of the Baltic as a distinct species from the cod of the North Sea. Although this Baltic cod occurs and supports a fishery as far up as the Finnish Gulf, and although its eggs have often been found in the deeper, saltest water of the Baltic, it cannot be considered as established that it breeds successfully in the Baltic, as would be inferred from Mr. Regan's statements on pages 5 and 6. Jacobsen and Johansen on page 21 of their article “ Remarks on the changes in specific gravity of pelagic fish eggs,” from which Mr. Regan quotes for support of his statements, state “ the majority of the pelagic fish eggs in the Belt Sea and the Southern Kattegat are present in the lower layers, and the same seems to hold good for the pelagic young of such species as cod and plaice.” The waters referred to are at the entrance of the Baltic. Also for the Baltic itself, Otterstrom ( “ Eggs and young of fishes in the Danish waters,” Rep. Dan. Biol. Sta., XIII, 1906) shows how the pelagic eggs are chiefly in the deep, salter water, and he states, “ In the inner parts of the true Baltic the upper water layers cannot float the pelagic fish eggs, or if so only quite exceptionally. On the other
hand, numerous pelagic fish eggs are found in the salt bottom-layers.” This deep salt water, in which the eggs and fry of the cod chiefly or altogether occur, moves into the Baltic from without at a rate estimated by Jacobsen and Johansen as between 0.04 and 0.12 miles per hour. Any cod fry occurring in the Baltic or in the waters at its mouth may well have been carried in with this inflowing water. Otterstrom on page 16 of the article mentioned above states, “ We have not up to the present found pelagic cod young in the true Baltic .... Cod and plaice thus do not develop in the true Baltic, which is probably connected with the extremely low temperature ruling in the deeper, egg-carrying water layers.” There are, therefore, good reasons for believing- that even in the case of the Baltic race of cod, brought forward by Mr. Regan, to show that cod would be expected to occur and to breed in Lake Melville, estuarial conditions with very low salinity of the surface water, and low salinity of the bottom water prevent development. There is no evidence whatever to show that the deep-sea cod which migrate to the Labrador coast for a short summer season, either live, breed or develop in the brackish and estuarial waters of Lake Melville.
Not only may species and varieties differ in the salinities that they frequent or can endure, but the individual fish may exhibit such differences from one stage to another of its life history. The eggs and fry of the salmon, as experiments by Dr. A. H. Leim and Mr. F. R. Hayes have shown, cannot endure salinities approaching those of the sea water frequented by the adults. That, since certain cod live, spawn, and develop in low salinities in the Baltic, therefore, cod in “ Hamilton inlet beyond the Narrows . . . are not deterred by the decreased salinity of the water ” (Regan, p. 8) is not a justifiable conclusion for the Labrador cod in view of the existence of racial differences, and is not necessarily valid even for the Baltic cod under the special conditions, which Lake Melville presents. In a region where life for European man depends almost wholly upon the cod fishery, the presence or absence of the cod in sheltered waters with easy conditions for fishing is certain to have been determined by frequent trials. As quoted in our “ Biology of Hamilton inlet, the Narrows, and Lake Melville,” the reports are unanimous that the true cod, Gadus callarias, does not extend even into the Narrows, and that it furnishes a fishery only in the outer part of Hamilton inlet. Such facts afford no ground for Mr. Regan's supposition on the basis of conditions in the Baltic that the true cod will be found in Lake Melville.
In the concluding paragraph of his article Mr. Regan assumes from analogy with other waters “ that a marine fauna and flora extends nearly to the mouth of the Hamilton river.” The Canadian investigations have demonstrated an admixture of sea water well to the head of Lake Melville. Under such a condition it would be expected that the waters of the lake would contain forms of life unable to live in strictly fresh water. Should all of these forms be called marine ? The various forms of plant and animal life show the most varied relations to salts dissolved in water. In no case are they able to dispense altogether with the salts. A very large proportion
of the earth's aquatic plant and animal life lives neither in the saltest water of the sea, nor in strictly fresh water (which contains but a minute percentage of salts), and presumably such forms are unable to endure either extreme. Some of these at least should be placed in an intermediate group or groups between the fresh-water and the marine forms, and there should be not only a brackish-water group, but also an estuarial group. Mr. Regan restricts the fresh water group and broadens the marine group with the result that he excludes from the former (p. 9) and includes in the latter (p. 5) fishes such as the salmon, Salmo salar, and the brook trout, Salvelinus fontinalis, that “ enter fresh water to breed.” This classification is inept seeing that these species can, and in fact do, either occasionally or usually, pass their whole life history in fresh water, and on the other hand cannot do so in the sea, being unable until well along in life to endure the salinity of the sea.
No hard and fast lines of division can be set. It would be expected that in Lake Melville the superficial or brackish water and the deep or estuarial water will have each to a certain extent its own characteristic forms of life, but also that each will have forms in common with one or more of the other kinds of water (including fresh water and sea water), or have either as strays or as more or less permanent residents forms properly belonging to one or more of the other kinds of water. Adult whitefish, Coregonus alba, and adult brook trout, Salvelinus fontinalis, are to be considered as fresh-water forms. Occasionally the adults are found in water with a salinity of 32 per mille or over, but that does not make the water fresh, but merely shows that at that stage they are able to endure such a condition. Similarly should certain forms that ordinarily go through their entire life-history in the sea be found nearly to the head of Lake Melville, it would prove no more than that they were able for a time at least to endure the brackish or estuarial conditions existing there. It would not invalidate the conclusion based upon the hydrographic conditions that have been described and upon the distribution of certain piscian, molluscan, and crustacean species, that the sea conditions and the sea fauna and flora, properly speaking, stop short of Lake Melville.
A. G. HUNTSMAN.