88 
BULLETIN OF THE UNITED STATES FISH COMMISSION. 
diameter of 3 mm., 6 to 12 oil-spheres which occupied the posterior (ventro-anterior 
in the figure) part of the vitellus when the embryo developed; 59 (60?) abdominal 
segments were developed. No. 8 had a diameter of 2 mm. and about 30 oil-spheres; 
the larva had 72 (73?) abdominal segments. No. 9 had a diameter of 2 mm., the yolk 
attached to the membrane by filaments; when the young developed, the oil-sphere 
occupied an anterior position and had the form of a club; 66 (67?) abdominal 
segments; larva much smaller than that of No. 6. No. 10 had a diameter of- 2.7 
mm., was without oil-sphere, and yielded a larva with 44 (45?) abdominal segments. 
All of these were taken between August and November, being more abundant in 
September and October. The earlier stages had a well-formed blastodermic callote. 
The yolk becomes well constricted after the blastodermic rim has passed the equator. 
The larvae had a number of characters in common, viz, an enormous fourth ventricle, 
a large oesophageal pouch, an elongate body with numerous abdominal segments, the 
position of the anus about halfway to the margin of the ventral fin fold, very large 
and striking teeth, and a series of pigment spots along the lower parts of the sides. 
When the larva is five or six days old it is slender and elongated, with a greatly 
compressed body, very transparent, and with little pigment. The vitellus is very 
elongated and diminishes from in front backwards. The intestine ends in the ventral 
fin fold a short distance from the body in a small accumulation of cells. The noto- 
chord is formed of a single series of segments. The mouth opens during the second 
day after hatching. The teeth develop rapidly. Three pairs are developed in the 
upper jaw. This dentition is absolutely exceptional among fishes. Contemporane- 
ously with the development of the mouth the choroidal pigment and five or six black 
pigmented spots form along the body. No noteworthy changes take place between the 
fourth and fifth days after hatching. Beyond this time Raffaele was unable to rear the 
eggs. He supposed these eggs to be those of eels, without more closely identifying 
them. Grassi, in his epoch-making researches in eel development, 1 identified Raffaele’s 
egg No. 10, without oil-spheres and with a diameter of 2.7 mm., as that of the com- 
mon European eel, Anguilla vulgaris. While unable to keep eggs like those described 
by Raffaele — which he secured at Naples — alive for many days, he showed that the 
newly hatched larvae described by Raffaele have essentially the character of Legyto- 
cephali. He states that females of eels can only mature in very profound depths, i. e., 
at least a depth of 500 meters. The male can mature in shallow water: 
Fertilization 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 sur- 
face. From the egg issue rapidly a prse-larva, which becomes a larva {Leptocephalus) with the anus and 
urinary opening near the tip of the tail. The larva then becomes a hemi-larva, the two apertures 
just named moving their position toward the anterior part of the body, which becomes thickened and 
nearly round. By further change the hemi-larva assumes the definitive or adult form. The larva, as 
well as the hemi-larva, shows a length of body much greater than that exhibited by the young Murse- 
noid of adult form into which they are transformed. By keeping specimens in an aquarium I was able 
to establish a diminution of more than 4 cm. during the metamorphosis. With regard to the greatest 
1 Grassi, B. The Reproduction and Metamorphosis of the Common Eel (Anguilla vulgaris), Q. J. M. S., vol. 39, page 371. 
Grassi, B., and Calandruccio, S. 
a. Ulteriori ricerche sulle raetamorfosi dei Murenoidi. Rend. Acc. Lincei, vr, p. 43. 
b. Descrizione d’ un Leptocephalus brevirostris in via di trasformarsi in Anguilla vulgaris. L. C. pp. 239, 240 (Trans- 
lation in Nature, LVi,p.85). 
c. Reproduzione e metamorfosi della Anguille. Giorn. Ital. Pesca e Acqui., 1887, Nos. 7, 8. (Abstract in Monit. Zool. 
Ital., vin, pp. 233 and 234.) 
