302 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1924 



other years they may be a little larger. They represent the last or 

 youngest portion of the I group, the great majority of which have 

 already moved away from the area. 



From our investigations with the Tlior in 1905-1906, it will be 

 remembered that the full-grown larvfB occur in early summer out- 

 side the coastal banks to the west of Europe. They vary in length 

 from 60 to 88 mm.; in June, 1905, the average was about 75 mm. 

 (fig. 2). In the same month the great bulk of the O group, averag- 



m.nu 

 44 



42 



40 



38 



36 



34 



32 



30 



28 



26 



24 



22 



20 



18 



16 



14 



12 



10 



8 



6 



4 



Fig. 10. — European Bel iAnguilla vulgaris) 



Western Atlantic (west of 50' 

 O group and three specimens of I 



long. W.), "Dana" Stations 935-948, April, 1921; 

 jroup. 



ing 25 mm. in length, are still on or near the breeding grounds. 

 During the journey, then, from here to the shores of Europe, these 

 larvae grow on an average 50 mm. Plotting the lengths for the 

 different months in a graph, we find that the larvae take on an aver- 

 age two years to grow so much (fig. 11). The full-grown larvae in 

 Figure 2 from June, 1905, thus represent the II group, and are, on 

 an average, two years older than the 25 mm. lar\^8e from the western 

 Atlantic shown in Figure 8 and on Plate 4. 



