BREEDIXG PLACES OF THE EEL SCHMIDT 



301 



The measurements will be seen from Figure 8, showing one, and 

 Figure 10, showing three of these larvae among the O group. The 

 graph, Figure 0. also indicates the lengths of the largest, specimens of 

 the O groups, which, as mentioned, varied at this season from 7 to 37 

 mm. It will be noticed that the millimeter scale shows a distinct 

 interval between the O group and the group of individuals between 

 40 and 50 mm. In June it lies about 38-39 mm., being then but 

 slight; in the spring, on the other hand, when the O group is much 

 smaller, the interval between the two groups is, of course, far more 

 pronounced (see fig. 10). There can thus be no doubt that the group 

 of 40-50 mm. length represents the remainder of the previous year- 

 class (the I group) : individuals which have not yet succeeded in 

 moving any considerable distance from the breeding-grounds. In 

 Figure 9 then, we have the uppermost portion of the O group and 

 the lowest portion of the I 

 group taken at the same time 

 and place; the figure thus 

 serves very satisfactorily to 

 show the limit between the 

 two year-classes in the month 

 of June. The Dana stations 

 in July, 1920, also, in the outer 

 parts of the breeding area, 

 show a distinct interval be- 

 tween the O and I groups; 

 here, however, it is found a 

 little higher up the scale, on 

 account of the growth which 

 has taken place. Even in Sep- 

 tember there is a trace of what 

 is probably the same at the Margrethe station 1027, south of the New- 

 foundland Banks, the interval in this month lying at about 45-47 mm. 

 length (fig. 4, p. 291). 



"We are now enlightened as to the sizes of the larvae in the western 

 xVtlantic at the different seasons. The larvae found here, i. e., west 

 of long. 50° "W., are almost without exception under 50 mm. in 

 length. They belong to the two ^"oungest year-classes, the O group 

 being by far predominant in point of numbers. Its average length 

 in April is about 12 mm., in June about 25 mm., and in October 30-40 

 mm. During the second half of the year the bulk of the O gi-oup 

 move away from the breeding area, but a number of individuals — 

 the numbers varying from year to year — do not manage to get away, 

 and we find them, then, in the spring and early summer as the I 

 group, especially in the northern part of the area, about latitude 30° 

 X. In June, 1920, the average length of these was 43-44 mm.; in 



mjTt 



44 



42 



40 

 38 



36 

 34 

 32 



Fig. 9. — European Eel (AnguiUa vulgaris) 

 Western Atlantic (west of 50° long. W.), 



" Dana," June, 1920. 

 O group and I group 



Showing limit between 



