TRANSACTIONS OF SECTION D. 411 



corresponds fairly exactly to the periphery of the great anticyclonic move- 

 ment of the currents. In the lands bordering on the Southern Atlantic 

 the fresh-water eel is quite wanting, and this phenomenon I have sought 

 to connect with the presumably unfavourable temperature and salinity of 

 the sea there. 

 1908-09 and 1910. — In these years we made two cruises with the ' Thor ' in 

 the Mediterranean, the first in winter, the second in summer. On these 

 cruises we found not only all the Leptocephalus species mentioned by the 

 Italian observers, but also the quite young larval stages of several species : 

 for example, of the conger and of the nearly related Conger mystax, a 

 species special to the Mediterranean. 



Of both these species the author gave a series of figures, showing the 

 developmental stages. They greatly resemble each other in the earliest 

 preleptocephalous stages, and both lack pigment on the sides. They ari 

 easily distinguished, however, even in the youngest stages of scarcely one 

 centimetre in length. Thus, Conger mystax has a more pointed snout, 

 and the pigment spots on the gut are much denser; further, the position 

 of the anus is quite different. The newly hatched larva? of the common 

 conger are only found in summer, those of mystax in the beginning of 

 winter, from which we see that the two species spawn at different times 

 of the year. 



As our investigations were made both in summer and winter, the 

 growth of the conger larvae could be followed, and we found that they 

 grew about 5 cm. in the course of six months, and used one to two years 

 for the whole of their larval development ; this applies to the common 

 conger. 



For the first time, we now learnt where the conger spawn, as we ob- 

 tained the tiny, newly hatched larvae, which could not have gone far from 

 the places where they were hatched. The spawning-place is everywhere 

 in the Mediterranean, especially in the deep basins, and further in the 

 Atlantic, west of Gibraltar. Another point of great interest was, that the 

 youngest larvae of both conger species, of only about 1 cm. in length, 

 were only found at the surface, not in deep water. Here, for the first 

 time, we learnt that not only the fully developed, but also the quite small 

 larvae, normally belong to the surface layers. 



Whether this holds good for all existing eel-fishes I am unable, natur- 

 ally, to say, but on our cruises in the Mediterranean we found several 

 thousand eggs of eel-fishes, and all these occurred near to the surface. 

 Some species only occurred in the middle of the basins, where the depths 

 are. great, others again nearer to the coast, especially in the western part 

 of the Mediterranean, where masses of muraenoid eggs were found at the 

 surface over depths of about 100 metres. It appears, therefore, that some 

 species of eels spawn nearer the coasts than others. Unfortunately. 1 

 have as yet been as little able as others to determine the species to which 

 the various muraenoid eggs belong. 

 1911. — This year I have not made investigations with the ' Thor,' but several 

 Danish steamers which cross the Atlantic have fished for us with 

 apparatus constructed for the capture of the larger pelagic organisms. In 

 this way we have obtained a very valuable material. Many of the samples 

 taken contained eggs of eel-fishes. I have not been able to determine the 

 species, but these discoveries have great interest in several respects. In 

 the first place, muraenoid eggs had previously only been found in the 

 Atlantic only at a single spot off the coast of the United States, whereas 

 it now proves that they occur over enormous distances right across the 

 ocean, at the least 40° N. latitude in a northerly direction. The 

 places where the muraenoid eggs have so far been found are represented 

 here on a chart. It will be seen that great interest attaches to these dis- 

 coveries in another way, in that these muraenoid eggs occur for a great 

 part out in the middle of the central parts of the ocean, where the depths 

 are the greatest found in the Atlantic. It follows from this, that the eel- 

 fishes must spawn out here ; but as all the eggs are found at the surface, 



