April 15, 1920] 



NATURE 



197 



of the goods will be forthcoming so long as a demand 

 exists, but once it is regarded as offensive — or shall we 

 say indicative of a lack of good taste? — to wear such 

 things as the wings, heads, feathers, or bodies of 

 birds, the demand will cease and the trade, so 

 far as this country is concerned, disappear. Herein, 

 we think, lies a remedy far more effective than any 

 Act of Parliament, Walter E. Collinge. 



The University, St. Andrews, March 27. 



The Physiology of Migrations in the Sea. 



The nat-tishes of Northumberland in the immature 

 condition migrate more or less inshore in summer 

 and offshore in winter. Flounders are relatively static, 

 plaice migrate offshore to the north-east and dabs to 

 the south-east. The migration is not, as a rule, con- 

 spicuous, and, so far as the young stages are con- 

 cerned, might be regarded as not taking place. 



With approaching maturity, however, these three 

 species migrate far to the north. The flounders for 

 the most part reach the coast of Fife, and the plaice 

 deeper water ofT the Forth and the Scottish coast to 

 the north. The dabs do not appear to migrate so far 

 to the north as the plaice, but we have a record of 

 one that migrated so far as St. Andrews Bay. Fulton 

 has shown that the Moray Firth plaice migrate to the 

 north, and even to the Atlantic. 



The migrations may be said, therefore, to be a 

 series of seasonal inshore and ofTshore movements, 

 followed by a marked contranatant journey for spawn- 

 ing. After spawning the spent fish resume the 

 seasonal migrations, and become then, more obviously, 

 summer inshore migrants. 



We have thus plainly two factors at work : one 

 external, which may be associated with temperature, 

 the other internal, which we at once conclude to 

 be due to the action of an internal secretion. The 

 seasonal migrations are obviously independent of the 

 spawning migration, and may be' said to be produced 

 by hydrographical conditions and the contranatant 

 ability of the fish. Under the influence of the spawn- 

 ing impulse fish migrate usually to a great, and some- 

 times to an immense, distance'. The effect is strong 

 enough to force the eel to descend from fresh 

 water to the sea, and thence to mid-ocean, and to 

 impel the salmon from the sea to the river, and, in 

 spite of difficulties, to the spawning-ground. 



The spawning migration is not always so plainly 

 marked, but these considerations go to show that all 

 fish migrations are of a similar character, a general 

 seasonal series of movements affecting all, and a 

 special migration under the dominating influence of 

 an internal secretion or hormone, which, proceeding 

 from the developing gonad, is carried bv the blood to 

 the nervous system. With reference to the species 

 referred to above, it can be said that the hormone 

 begins to exert its influence about autumn or the later 

 months of the year, and continues its effect during 

 the whole period of ripening. It is periodic in its 

 manifestations, and the call, when it comes, is im- 

 perative. Only in special circumstances, as lack of 

 water, say, in the river, can the spawning migration 

 be said to be modified by hydrographical or other 

 physical conditions. The distinction between the two 

 kinds of migration must be clearly kept in view if 

 we are to understand and appreciate the results of 

 marking experiments. From, say, November to the 

 spawning season mature plaice are contranatant 

 migrants; after spawning thev are denatant, or 

 usually so, until the winter. 'The large number 

 of records which have been accumulated, resulting 

 NO. 2633, VOL. 105] 



from the investigations of past years, should be re- 

 considered with this in mind. 



It is interesting to observe that the only invertebrate 

 of the migration of which we have direct proof 

 behaves almost exactly like the plaice and the flounder. 

 The common edible crab {Cancer pagurus) migrates 

 inshore in summer and offshore in winter with the 

 greatest regularity. Maturity impels the female to 

 become a contranatant migrant. The females migrate 

 from the Northumberland coast to the southern coast 

 of the Firth of Forth, some of them still further to 

 the north, even to the Moray Firth, the general results 

 indicating a direct relationship between size and dis- 

 tance. The hormone is therefore secreted in the crab 

 by the developing ovary, and it reacts in exactly the 

 same way as that of the fish. The experiments have 

 clearly proved that the migration does not occur until 

 the winter before the season of spawning, and in this 

 respect the crustacean and the fish are in agreement. . 

 It takes place during the offshore winter migration 

 and in deep water, but the effect is differential, the 

 male not migrating. It is not necessary for the male 

 to migrate, as the migration takes place after pairing, 

 even a year or two years after. This appears to indicate 

 that the internal secretion is under control or may 

 be withheld in response to evolutionary necessity. 



Dr. Gurley, in the American Journal of Psychology 

 (1902 and 1909), brought under review the indications 

 of the intoxication of the central nervous system by 

 internal secretions as explaining the spawning migra- 

 tions of fresh-water fish in North America ; so that the 

 point is not new. We do not know very much about 

 the internal secretions, but we know enough to be 

 able to say that they act directly and quickly as an 

 intercommunication between organs with or without 

 reference to the nervous system. In the sea the 

 effects are indicated by migration in the case of such 

 animals as are capable of making migrations, but it 

 is obvious that in many cases the internal secretions 

 derived from the gonad have somatogenetic as well 

 as mental effects, as in the development of secondary 

 sexual characters. 



The developing gonads of fish and the crab offer 

 interesting material for the investigation of internal 

 secretions by a biochemist. My main object, however, 

 is to indicate that we already know the general facts 

 and laws of migration, that marking must be 

 done intelligently and the results read with due con- 

 sideration of the laws, and more especially that the 

 spawning migration is due to an intoxication of the 

 central nervous system, and brings about a migratory 

 result independent of temperature, salinity, and every 

 other hydrographical condition. 



Alexander Meek. 

 Armstrong College, Newcastle-upon-Tyne, 

 March 30. 



Muscular Efficiency. 



Whbn muscular force is exerted, power is expended 

 and fatigxie is produced, even when the muscle 

 remains stationary. Again, when no external force 

 opposes the contraction of the muscle, physiological 

 causes set a limit to the speed at which contraction 

 can take place. In both cases the whole power ex- 

 pended is lost in so far as the production of useful 

 work is concerned. When there is no velocity the 

 power is used in maintaining the stress, and when 

 there is no resistance, in maintaining a constant 

 velocity. ' 



In all ordinary muscular operations both these 

 sources of power leakage act simultaneouslv but in 



* This loss is independent of «ny power lost in the acceleration of the parts. 



