— 274 — 



CONTENTS page 



Preface 137 



Section I 



Introduction: Summary of the earlier investigations on the 

 developmental history of the eel 



A. The older eels 



1. Male and female eels 138 



2. Yellow and silver eels 139 



3. Migration of the breeding eels to the sea , ■ 14.0 



4. Discovery of the common eel in the open sea 144 



B. The young stages of the eel 



1. The Leptocephali the young forms of eels 146 



2. Distribution and occurrence of the larvae of the common eel 151 



3 . Eggs of eels taken in the sea 155 



Section II 



The present investigations and observations 



1. Investigations of the "Thor" in 1903 and 1904 i 157 



2. Investigations of the "Thor" in 1905 159 



3. The larvae of the eel {Lepiocephahis brevirostris) and their biology 162 



a. The appearance of the eel larvae in June 163 



b. The appearance of the larvae in September and their metamorphosis '. 166 



c. The mode of life of the eel larvae [Lepiocephahis brevirostris) 176 



d. Bathypelagic fish eggs (floating in deep water) are common in the Atlantic Ocean 179 



4. Distribution of the larvae of the eel (Lepiocephaitis brevirostris] in the Atlantic Ocean 182 



a. Our discovery of the larvae 182 



b. General remarks on the distribution of the eel larvae 186 



c. Conclusions to be drawn from our discovery of the larvae with regard to the spawning places of the eel 187 



d. Other species of Leptocephali 189 



e. List of the catches of Leptocephahis brevirostris by the "Thor" in 1904 and 1905 194 



5. Inward migration of the young eels from the Atlantic Ocean to the coasts of West and North Europe. 



a. General remarks on the phenomenon of ascent 196 



b. Elvers as food 197 



c. Migration of the elvers into fresh water on the West and North European coasts 204 



d. Occurrence of young eels in the sea 213 



e. Conclusions to be drawn from the material with regard to the inward migration of the young of the eel 217 



6. Why the eel does not propagate in the neighbourhood of the continental coasts of North Europe 231 



7. Biology of the eel in comparison with that of other fishes 234 



8. Discovery of a fully ripe male of the common eel {Anguilla vulgaris) in shallow water 238 



9. Relation between the European and American eels {Angiiiila vulgaris and chrysypa) 239 



a. Adult fishes -.- 239 



b. Young Stages 243 



Section III 

 Importance of the present investigations for the eel fisheries in the Baltic countries 



and Denmark 245 



Appendix 249 



Section IV 



Resume 256 



Explanation of the Plates 264 



Beiträge zur Naturgeschichte des Aales (Auszug) 265 



Misprints and Corrections 273 



