10 



EINAR LEA. 



[REP. OF THE "MICHAEL SARS" NORTH 



Fig. 3. 



stages I and II, which correspond closely with Schmidt's 

 description. They are possibly a little smaller than the 

 annual series examined by Schmidt, the average length 

 of the larvae of stage I being 73-1 mm, (Schmidt's larvae 

 of 1905 being 75-21 mm and of 1906 7645 mm). Whether 

 this difference is casual or due to the scarcity of the 

 material, or to the lateness of the season (July and August), 

 or to the variation of different annual series, cannot be 

 determined. The average length of six individuals of 

 stage II is 70-6 mm. 



The geographical distribution of the larvae of the eel 

 is shown on fig. 3, the occurrence of prelarvae being 

 indicated by circles, of full-grown larvae by triangles, and 

 of metamorphosing larvae by squares. The map is divided 

 into four quadrants by lines crossing the Azores, one from 

 east to west, and the other from north to south, and it 

 is plainly seen that all the prelarvae without exception 

 were taken in the south-western quadrant, whereas all the 

 full-grown larvae except one, were caught in the north- 

 eastern quadrant. Further, all the metamorphosing larvae 

 were taken at depths less than 3000 metres (Stat. 98 where 

 all the larvae in stage II were taken is situated beyond 

 the 1000 metres line), whereas almost all the other larvae 

 and prelarvae were taken at depths greater than 3000 

 metres partly in the middle of the ocean. A third point 

 of interest is the fact that full-grown larvae were taken 

 very far west, one even at a point much nearer America 

 than Europe. If we compare this map with the map in 



Schmidt's paper, it is evident that Schmidt's 

 investigations were mostly carried on towards 

 the northern and eastern limits of distribution 

 of the eel-larvae, for they have been taken as 

 far south as 32° N., and as far west as 48° W. 

 (prelarvae) and 40° W. (full-grown). 1 ) 



Fig. 4 shows the number of larvae of the 

 eel taken at different depths during the cruise, 

 and it is seen that most of the small larvae 

 were taken at a depth of 50 metres, whereas 

 most of the large larvae were caught at 100 

 and 150 metres. It seems necessary to conclude 

 from these catches that both the big and the 

 small larvae live quite near the surface, most 

 of the prelarvae having been taken at night- 

 stations while most of the full-grown larvae were 

 caught at day-stations. Schmidt's observations 

 prove that the larvae of the eel, like very many 

 other animals, undertake daily vertical migra- 

 tions, living at greater depths during the day 

 than at night. According to Schmidt (Remarks 

 on the Metamorphosis etc 1909 p. 14) 



the full-grown larvae occur during the night in great 



numbers at 30 metres below the surface. 



The "Michael Sars" material does not throw much 



light on the problems concerning spawning place and 



metres 



50 



100 



150 



200 



300 



500 



not fullqrown larva 

 fullgrown » 



metamorphosing » 



• A ▲ 



Fig. 4. 



period, migrations, age, and growth of the eel, seeing 

 that it does not contain eggs, newly hatched larvae, or 

 spawning eels, but it may possibly be valuable in forming 

 working ideas for future investigations. The material must, 



') In a paper from 1912 (no. 31 in the literature list) Schmidt has accounted for further Danish investigations regarding the eel-larvae. 

 They support in the main points the conclusions drawn here. 



