November 24, 19 10] 



NATURE 



\0' 



which eel-larvae Were found, the figures indicating the 

 number of larvae caught at each place. The chart shows 

 the existence of eel-larvae over the greater part of the 

 Korth Atlantic between North Africa and North America. 

 The excellent Danish irtvestigations planned by Dr. C. G. 

 Joh. Petersen, and carried out by Dr. Johannes Schmidt, 

 succeeded with Dr. Petersen's young-fish trawl in catching 

 eel-larvae over depths mostly of looo metres along the 

 continental slope from Shetland to Gibraltar. On the 

 American side, larvae of the American eel (^XnguiXla 

 chrysypa) have already been found over the continental 

 slope off the United States. The catches made by the 

 Michael Sars now have this particular interest, that they 

 prove the distribution of the larvae, not only on the slopes, 

 but also in mid-ocean over the greatest depths, both over 

 the deep eastern and western basins and over the Azores 

 ridge separating them. 



.\ccording to their length, the larvae may be divided into 

 two distinct groups, one including specimens of 41 to 

 60 mm. in length, the other those of 66 to 82 mm. (see 

 Fig. 2). All the specimens belonging to the first group, 

 twenty-one altogether, were found at the stations south of 

 the Azores, marked by a cross, and all those belonging 



Length 



m mm. 



40 



-«■ 



iO- 



5S 



«0 



60- 



70- 



70- 



80 



85 



Number of individuals 



Southern Group 

 21 dndividuQls 



Northern 6roup 

 25 c3ndividuQl5 



Fig. 2. 



to the group of larger individuals were caught at the 

 stations north of the Azores, marked by a circle. In order 

 to control the determination of the larvae, my assistant, 

 Mr. Einar Lea, has counted the myomers of all the 

 lan,aE, and the results are given, for both groups 

 separately, in Fig. 3. All the individuals — of either group 



have a number of myomers not exceeding the limits, 

 HI to 119, given by Dr. Schmidt as characteristic of the 

 larvae of the common eel (Leptocephalus brevirostris). 

 They are thereby distinguished from the larvae of the 

 A.merican eel iAnguilla chrysypa). For the larvae of the 

 latter Eigenmann and Kennedv give the number of 

 myomers as 105 and 108, and Dr. Schmidt has, by count- 

 ing the vertebrae, fixed the limits at 104 and no. 



The larvae of the common European eel previously found 

 by Dr. Schmidt in the North .Atlantic were all either full- 

 grown leptocephalic larvae or in subsequent stages of trans- 

 A^i'i'"^''^"" ^^- ^chrn'<^t describes five different stages. 

 All the larvae found by the Michael Sars north of the 

 Azores belong to one or other of these stages. Outside 

 the continental slope no larvae of the transformation stages 

 were found, but only full-grown leptocephalic larv^ corre- 

 spondmg to Dr. Schmidt's stage i. This holds good both 

 NO. 2143, VOL. 85] 



for the lar\-a found in April in the Bay of Biscaj: and for 

 the larvae found in July between Newfoundland and 

 Ireland. On the continental slope off the British Isles, 

 however, larva in transformation stages (Schmidt's stages 

 2 and 3J were found. 



The lar\ae found by the Michael Sars south of the 

 .Azores are all smaller than the full-grown leptocephalic 



Fig. 



larva. I understand them to be stages in the develop- 

 ment from the ovum to the full-grown larva. All have 

 teeth which in everA' essential correspond to those charac- 

 terising stage I, as described by Dr. Schmidt. I must 

 therefore consider the larvae caught south of the .Azores to 

 be younger than any before found. 



So far, no other stages have been discovered among 

 the materials secured by the Michael Sars. More material 

 is therefore needed to give a full explanation of the facts 

 stated above. As, in the numerous Danish investigations 

 and in all the hauls made by the Michael Sars, no single 

 specimen belonging to the youngest stages has been found 

 in the area north of the Azores, the conclusion seems 

 natural that the spawning area of the eel must be sought 

 in the southern central part of the North Atlantic. How- 

 ever, the spawning^ area can only be located by the evidence 



jU 



Jtr 



X>. 



d. 



Fig. 4. — Eel-larvae found by Mkkatl Sars ; a-c, caught south of the 

 Azores ; d, north of the .\zores ; a, the smallest larva found ; d, a fuil- 

 gro«n larva as the youngest previously found. .\11 the figures are 

 copied from photographs. Nat. size. 



of ova. So long as the eggs have not yet been discovered 

 the spawning area must also be considered as unknown ; 

 but it is natural to look for it in the neighbourhood of 

 those localities where the youngest stages have been found. 

 The discovery of the ova would not only give information 

 about the geographical position of the spawning area, but 

 also about the ages of the different lar\3e hitherto found. 

 It may then be possible to understand the distribution of 

 the different stages — the youngest south and the eldest 



