Marcu 18, 1897 | NATURE 467 
the common eel. They had not been able to follow the- 
entire metamorphosis in one and the same specimen; 
; ; but they had verified the most important changes in, 
alg te first Leptocephalus was discovered in 1763, when | specimens kept in confinement, and compared all the 
a specimen was taken near Holyhead, by Mr. | organs in various stages with those in the perfect form. 
William Morris, and sent to Pennant. Since that time | The greatest length of the larva is 8 cm., or 3; in., and 
numerous specimens, having similar characters, have | the reduction after transformation is never more than, 
been obtained on the shores of Britain, in the Mediter- | 3 cm., so that the smallest elver, or young fully-developed 
ranean, and at the surface of the ocean in various parts | eel, is 2 in. long. 
of the world. The chief peculiarities of these creatures, A fuller account of this most interesting investigation 
which have long been considered much more extra- | was communicated by brof. Grassi to the Royal Society 
ordinary than they really are, are the following. The | last year, and is published in the Pvoceedings of 
THE DISCOVERY OF THE LARVA OF THE 
COMMON EEL. 
Pic. 1.—Leptocephalus Morristi, the larva of the Conger. (After Couch.) 
body is several inches in length, thin and of uniform | December 1896, and also in the Quarterly Journ. Mic. 
breadth like a piece of ribbon, very transparent, and Sc’. of November 1896. It is well known that in the 
unpigmented. The head is small in proportion; there | Straits of Messina strong currents and whirlpools occur. 
are pectoral fins, but no pelvic, and there is a narrow fin To the existence of these disturbances of the water, the 
running along the edge of the body, above and below, to occasional occurrence of various stages in the develop- 
the tail. The blood is not red, and there is no air- ment of Murzenoids in the surface water is to be attri- 
bladder. Internally the body consists largely of a buted. As the Leptocephali are captured in company 
peculiar gelatinous tissue. with fish of various species known to belong to the deep- 
The suggestion that the Lef/ocephal? were the normal — sea fauna, it is inferred that the spawning of the eel 
larvee of fishes of the eel family, was first made by the and other Murzenidz, and the development of the eggs 
American ichthyologist, Gill, in 1864. In 1886 Yves and larvee, take place normally at great depths—at least 
Delage proved experimentally that Z. AZorristi changed 500 metres (250 fathoms)—and that the larvee are carried 
into a young conger. to the surface with deep-sea fishes by the movements 
of the water just mentioned. Specimens of Murena 
helena with ripe eggs, and of adult eels, both male and 
female, have also been captured under the same circum- 
stances. In these adult eels the generative organs are 
sometimes more developed than in specimens otherwise- 
obtained, and in some of the males ripe spermatozoa 
a 
SISWSSSs 
have been observed for the first time. A ripe male 
Fic. 2.—Leptocephalus brevirostris, the larva of the Eel. (After the conger was described in 1881 by Otto Hermes, and 
5 
original figure in Kaup’s Catalogue of Apodal Fish, 1856.) Saal aTS kept aire by ie present ayia anita 
In 1892 Grassi and Calandruccio published their first | Plymouth Aquarium, but ripe male eels had never before 
paper on these forms, giving a brief and summary been obtained. ; 
account of the results of observations at Catania. These mature, or nearly mature, eels are remarkable 
They had obtained a large number of living speci- | for the large size of their eyes ; and similar specimens, 
mens from the harbour of Catania, and had suc- | previously obtained from deep water, were described as 
ceeded in keeping them alive for varying periods in | distinct species by Kaup. The mature male conger is 
aquaria. The specimens belonged to several of the | also distinguished by the greater size of its eyes. In the 
“species” which had previously been distinguished and | mature eels, also, the skin of the belly is silvery, not 
named, and their metamorphosis into specimens of | yellow, as in river eels. : 
various species of Murzenidie was traced with complete, Raffaele, in his valuable paper on the pelagic eggs 
or nearly complete, continuity in a number of cases. | and larve of fishes in the Gulf of Naples, published in 
Thus the complete metamorphosis of Z. Morrisit into | the Mittheilungen of the Naples Station in 1888, de- 
GC Oo a Sl ERE ARN AU RN AUUURRRUUUD SRUREREUESEAUEREUUUERSS SCS G ant ae 
Le J 
Fic. 3.—Young Leffocephalus, hatched in the aquarium, as it appears after the absorption of the yolk. Actual length, 9*1 mm, 
(After Raffaele.) 
young congers was traced in 150 individuals, larvze 5 in. | scribed five different kinds of pelagic eggs which had’ 
long being reduced to conger of only 3 in. L. diaphanus certain common characters, and which, in his opinion, 
became Congromurena balearica, L. Kollikeri, Yarrellit, possibly belonged to various species of the Murzenide. 
Haeckeli, and other forms proved to be all stages in the Raffaele described the larva hatched from one of these 
normal development of Congromurena mystax,and L. eggs, and it has the essential characters of a Lepfo- 
Kefersteini changed into Ophichthys serpens. cephalus. Grassi considers that one kind of these eggs, 
Leptocephali are most frequently taken in the Straits | which has no oil-globules, is that of the common eel. 
of Messina, and amongst the forms there obtained is But he believes that the eggs, like the larvee, are only 
one named Z. brevirosiris, which is remarkable for its | occasionally brought to the surface, and that they 
small size, and the entire absence of specks of pigment. normally remain at great depths. : ay 
In 1893 Grassi and Calandruccio announced that they It is a curious fact that the larve, now identified as 
had proved that this particular form was the larva of | those of the eel, are found in greatest abundance in the 
NO. 1429, VOL. 55| 
