— 155 — 



3- Eggs of eels taken in the sea. In 1888 the Italian Raffaele' described 

 5 species of peculiar pelagic fish eggs from Naples Bay. These eggs were characterised 

 in contrast to all other pelagic lish eggs by their unusual size (between 2 and 3 mm. in 

 diameter). They had further a large perivitelline space, segmented yolk and usually a 

 large oil-globule. On hatching they gave very elongated larvae, which soon obtained a 

 very characteristic teeth equipment. Raffaele refers these large pelagic eggs to the eels, 

 but it was not possible for him to determine to which of the eel species the 5 different 

 kinds of eggs belonged, and he was therefore content to give them the different numbers 

 from No. 6 to No. 10. 



These eel eggs of Raffaele were mentioned later by Grassi and Calandruccio, who 

 subjected them to renewed investigation. They confirmed Raffaele's supposition that 

 they were eel eggs and say further that Raffaele has probably placed 2 species under 

 his Muraenoid egg No. 10, one of which is the common eel. They do not however 

 bring forward any proofs for the correctness of this conclusion, and it should be noted 

 that we do not know with certainty the developmental stages which pre- 

 cede the Leptocephalusstage (preleptocephalic stages) neither in Anguilla nor in 

 any other species of eel. On the other hand we thus know that characterisdc large 

 pelagic eggs occur at certain places in the Mediterranean, which belong to various species 

 of eels not definitely determined 3. Whether these undoubtedly pelagic Muraenoid eggs 

 belong normally to the surface or to greater depths has not been fully determined. 

 Raffaele never found them at an earlier stage than where the gastrula was already formed. 

 GrassH believes that "fertilisation takes place at great depths; the eggs float in the 

 water; nevertheless they remain at a great depth in the sea, and only exceptionally, 

 for unknown reasons, some of them mount to the surface." Eigenmann 3, who has 

 also investigated the eggs of eels, remarks on this: "Grassi also secured the eggs of 



1 Raffaele, Le Uove Gallegianti e le Larve dei Teleostei nel Golfo di Napoli (Mitth. aus der Zool. Stat, 

 zu Neapel, VIII, p. 1—84, tav. 1 — 5, 1888). 



2 On .the contrary Cunningham's and Fulton's comparative studies of the ovarian eggs and of ripe free 

 eggs in a number of species seem to show that the Italian authors are mistaken when they refer RaffAELE's 

 egg No. 10 (devoid of oil-globule) to the common eel {Anguilla vulgaris), the ovarian eggs of which have oil- 

 globules. The investigations of both these British authors show, that in the species where the ovarian eggs have 

 oil-globules in the perinuclear zone the ripe eggs are also furnished with oil-globules. FuLTON thus writes (T. W. 

 Fulton, On the growth and maturation of the ovarian eggs of teleostean fishes, Ann. Rep. of the Fishery Board 

 for Scotland, for 1897, Part III, 1898, p. 97 — 98, footnote): "The presence of numerous, perinuclear oil globules in 

 the ovarian egg of the common eel points to the existence of one or more oil-globules in the mature egg. It 

 would therefore appear that Grassi's identification of Raffaele's undetermined species No. 10, which is devoid 

 of oil-globules, with Anguilla vulgaris, is very doubtful." 



3 Outside the Mediterranean eggs belonging to eels have only once been found in the sea, namely off the 

 coast of North America. This discovery is described by Eigenmann in a paper entitled: "The egg and deve- 

 lopment of the conger eel" (Bull, of the U.S. Fish Commission, vol. XXI, for 1901, Washington, 1902, p. 37— 44), 

 The eggs were taken pelagically (on the surface?) on July 31st 1900 on "the tile-fish grounds about 30 miles 

 south of South Shoal.'' They were allowed to hatch and some of the larvae (see Fig. 5) were kept alive until 

 the night between the 13th and 14th of August. Whilst there is no doubt for several reasons that these large 

 2'4 — 2*75 mm. eggs belonged to an eel, quite possibly even to the conger, there is however no real proof to 

 show that the latter is correct, even though the authors are very probably correct when they say, p. 44 : "The 

 present eggs may provisionally be identified as those of the conger." 



4 Grassi, The Reproduction and Metamorphosis of the Common Eel {Auguilla vulgaris). Proceed. Royal 

 Soc, vol, LX, No. 363, p. 262, 1896. 



