300 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1924 



As mentioned, the average length in June was about 25 mm., and 

 the great majority of larva? of this size were found to occur near 

 the surface — from a depth of about 50 m. to the surface itself. 

 The younger larva? (7-15 mm. long) were taken somewhat deeper, 

 at depths ranging from about 300 to about 75 m. ; but it must be 

 borne in mind that the depth of the ocean here is over 6,000 m. 

 We may, therefore, assert that the larvas of the eel, even at these 

 early stages of development, are true pelagic organisms, pertain- 

 ing to the upper water layers, as the 1905 investigations had shown 

 was the case with the full-grown larvae. 



A closer investigation of the sizes of the larvae from the Dana 

 stations in the western Atlantic is of interest. The figures provide 



Fig. 8. — European Eel (Anguilla vulgaris) 



Sizes of larvse caught in a single haul of two hours' duration at " Dana " station 871 

 (lat. 27° 15' N., long. 61° 35' W.) in the western Atlantic, June 27, 1920; depth 

 about 50 m. (same haul as that represented in fig. 10). The largest specimen shown 

 belongs to the I group, the remainder to the O group. 



a far sounder basis for determining the age of the larvae that we 

 had before. Figure 10 shows the sizes of the youngest year class 

 (the O group) in April, 1921, and Figure 8 the O group in June, 

 1920. The measurements from June are from specimens taken in 

 a single haul. If we include the entire material from the Dana 

 stations in June, 1920, we find that the O group varies from 7 to 

 37 mm., with an average length of about 25 mm. We have a very 

 large quantity of material from the month of June, between four 

 and five thousand specimens, so that the average length of the group 

 for this month is determined with a high degree of accuracy. 



Now it has been noticed for several years, that in spring a few eel 

 larvae, between 40 and 50 mm. long, appear in or near the spawning 

 area in the western Atlantic. In June, 1920, also, some of these 

 larvae — 78 in all — were taken by the Dana, more especially in the 

 northern part of the area. 



