president's address. . ^ l , 11 



of great value are obtained — such as the investigation and prediction 

 of tidal phenomena. We are now told that theories require re-investi- 

 gation and that published tables are not sufficiently accurate. To 

 take another practical application of oceanographic work, the ultimate 

 causes of variations in the abundance, in the sizes, in the movements 

 and in the qualities of the fishes of our coastal industries are still to 

 seek, and notwithstanding volumes of investigation and a still greater 

 volume of discussion, no man who knows anything of the matter is 

 satisfied with our present knowledge of even the best-known and 

 economically most important of our fishes, such as the Herring, the 

 Cod, the Plaice and the Salmon. 



Take the case of our common fresh-water eel as an example of how 

 little we know and at the same time of how much has been discovered. 

 All the eels of our streams and lakes of N.-W. Europe live and feed 

 and grow under our eyes without reproducing their kind — no spawning 

 eel has ever been seen. After living for years in immaturity, at last 

 near the end of their lives the large male and female yellow eels 

 undergo a change in appearance and in nature. They acquire a silvery 

 colour and their eyes enlarge, and in this bridal attire they commence 

 the long journey which ends in maturity, reproduction and death. From 

 all the fresh waters they migi'ate in the autumn to the coast, from 

 the inshore seas to the open ocean and still westward and south to the 

 mid-Atlantic and we know not how much further — for the exact 

 locality and manner of spawning has still to be discovered. The 

 youngest known stages of the Leptocephalus, the larval stage of eels, 

 have been found by the Dane, Dr. Jobs. Schmidt, to the west of 

 the Azores where the water is over 2000 fathoms in depth. These 

 were about one-third of an inch in length and were probably not long 

 hatched. I cannot now refer to all the able investigators — Grassi, 

 Hjort and others — who have discovered and traced the stages of growth 

 of the Leptocephalus and its metamorphosis into the ' elvers ' or young 

 eels which are carried by the North Atlantic drift back to the coasts of 

 Europe and ascend our rivers in spring in countless myriads; but no 

 man has been more indefatigable and successful in the quest than 

 Dr. Schmidt, who in the various expeditions of the Danish Investigation 

 Steamer Thor from 1904 onwards found successively younger ajid 

 younger stages, and who is during the present summer engaged in a 

 traverse of the Atlantic to the West Indies in the hope of finding the 

 missing Hnk in the chain, the actual spawning fresh-water eel in the 

 intermediate waters somewhere above the abysses of the open ocean." 



° According to Schmidt's results the European fresh-water eel, in order to 

 be able to propagate, requires a depth of at least 500 fathoms, a salinity of 

 more than 35.20 per mille and a temperature of more than 7° C. in the required 

 depth. 



