Organic Polarity Some Ecological and Physiological Aspects

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Abstract
The enormously greater differentiation of the tropical faunas provides circumstantial evidence that the warmer parts of the earth are the most likely cradle for the origin of species. The study of the chromosomal mechanism and the breeding expts. of geneticists have shown that the segregation of certain genes and the production of a race that will thereafter remain true, may readily occur. A case is cited in which temp. has been held to have affected nuclear division with a resultant alteration in the primary sex ratio. In these circumstances we should not find it difficult to expect special segregations of genes or "mutants" to take place more often in lower latitudes. Such a view of the origin of spp. implies a segregation and differentiation of characters already present in the original stock and is therefore analytic rather than synthetic. During that part of the earth''s history during which living organisms have been present, there have been warm and cold periods (glacial and inter-glacial epochs) and it may well be that the greatest numbers of new spp. were formed in the warm interglacial epochs. A more immediate application of the deductions applies to the problem of over-fishing. In the North Sea, a smaller yield of food-fish is being made for unit time and gear than was formerly the case, and most fishery scientists are agreed that over-fishing is the cause of this condition. Apart from the gross decline of the yield there has also been a change in the relative importance of the spp.; e.g., cod, haddock, and halibut[long dash]all northern fish[long dash]have declined steadily in the post-war yrs.; but 2 southern spp. have increased in importance. The whole catch has declined because the northern spp. are still the greatest part of the yield. This qualitative change might have been of no significance had it not been recently pointed out by Scherhag that a continuous warming up is going on in the northern hemisphere. In these circumstances it seems improbable the reduced yield per unit of effort in the North Sea is due solely to over-fishing. The possibility that the rising temp. is causing an increase in the specific complexity and a decrease in individual size and total bulk remains to be examined as at least a contributory cause.

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