46 THE SCOTTISH NATURALIST 



I do not doubt ; that it tends to go astray in these far- 

 reaching and dwindling currents seems also clear ; but that 

 it merely drifts passively and helplessly along on its 

 involuntary voyage, though it is far from improbable, is yet 

 more, I think, than we can safely assert, or more than the 

 present evidence can confirm. 



One very curious point in the history of the Sun-fish 

 remains to be mentioned. The little Leptocephalus-larvae 

 of the Eel have been found in its stomach, often in multitudes ; 

 and some writers have even believed that these constitute 

 its chief nutriment (cf. Nature, xciii., p. 166, 1914). Now we 

 know, from the work of Dr Johann Schmidt, and from the 

 later and minor papers of Mr Einar Lea {Murcenoid Larvcs of 

 the Michael Sars, 1 Bergen, 191 3) and Dr Bowman (Sc. Fish. 

 Bd., Sci. Investigations , No. 11, 191 3), that the eel-larvae 

 reach our western waters in early summer, about the month 

 of June, on their shoreward migration from the Atlantic ; 

 that from then till August, they are passing round the N.W. 

 and N. of Scotland (and doubtless also up the English 

 Channel) ; and that, metamorphosing as they go, they at 

 last appear, as " elvers," off our eastern coasts in November 

 and December, ready to ascend the rivers in spring. There 

 would seem, then, to be a close and even precise correspond- 

 ence between this periodic annual migration of the Lepto- 

 cephali and the appearance of the Sun-fish in our home waters. 

 In the case of this and other of the larger fishes, we are 

 often tempted to correlate the season and route of their 

 migrations directly with temperature and other physical 

 conditions; or even, like Dr Johansen, with the course and 

 route and actual motion of an ocean-current. But in this 

 particular case I am rather led to the conclusion that food 

 is the influence immediately at work, and that it is on the 

 smaller living food-organisms of the " plankton " that the 

 physical conditions have more directly operated. 



1 Koren and Collett also record large quantities of medusa? in the 

 stomach. 



