GENERAL BIOLOGY 



753 



Newfoundland to the Azores and Morocco only essentially larger 

 (and older) stages of these species were taken, as shown in the 

 case of the larvae of the common eel {^Leptocephalus brevirostris). 

 It has long remained a mystery where the common eel spawns. 

 No sexually mature individual has ever been found among the 

 millions of eels annually captured in the waters of Europe, 

 nor have the eggs or minute larvae ever been found. The 

 autumnal migration of the eel has, however, been known for 

 ages. During this migration the eels leave the rivers, lakes, 

 and closed waters of the sea 

 and make for open water, and 

 certain naturalists, like C. G. J. 

 Petersen, concluded that the 

 eel was actually an oceanic 

 deep-sea species. This idea 

 seemed all the more obvious 

 as the Italian scientist Grassi 

 had, in the Mediterranean, 

 proved Leptocephalus breviros- 

 tris to be the larva of the eel. 

 A marked advance in the solu- 

 tion of this mysterious problem 

 was made when Jobs. Schmidt^ 

 succeeded in capturing quanti- 

 ties of leptocephali along the 

 Atlantic slope of the coast 

 banks of western Europe. 

 Schmidt here found the fully 

 developed larvae, mostly ex- 

 ceeding 6 cm. in length, and all 

 the transition stages before the 

 leptocephali become " glass eels" 

 or elvers, which in spring invade 

 all the coasts of northern Europe, where they are well known. 

 During our cruise we found essentially smaller stages,^ down 

 to 4 cm., long, and we have thus been able to trace the series 

 shown in Fig. 550. In this figure the five lower stages are 

 taken from Schmidt's excellent account, the upper four stages 

 having been drawn from specimens captured by the " Michael 

 Sars," all magnified 1.4 time. The three upper figures 



^ See Schmidt, " Contributions to the Life-History of the Eel," Rapports et Proces-verbaux 

 dii Conseil international, vol. v., 1906. 



- See Hjort, " Eel-larvce from the Central North Atlantic," Nature, vol. Ixxxv. p. 104, 1910. 



% C 



LarvK of the 

 common eel. 



Fig. 551. — Measurements of Larvae of 

 THE Common Eel {Anguilla vulgaris). 



