Part III. — Thirteenth Annual Report 



average position of the anus is, in the young eel, nearer the snout than 

 in the adult. The ratio of the total length, to the distance from the 

 tip of the lower jaw to the anus was calculated, and it was found that 

 in the fifteen larger eels, of from 15*8-92'03 cm. in length, the ratio 

 varied from 2*22 to 2 - 54, while in the fourteen elvers (63-87*5 mm.) 

 the ratio varied from 2*37 to 2*72. In a young conger, 25*7 cm. long, 

 the ratio of the total length to the distance of the beginning of the 

 dorsal fin from the tip of the upper jaw was 5, while the ratio of 

 the total length to the distance between the tip of the snout and the 

 anus was 2*5. It is thus seen that in the conger while the dorsal fin 

 commences much further forward, the anus occupies a position coincident 

 with that of the anus in the Anguilla. * The continuous fin of the 

 elver is broadened sensibly at the tail; the rudimentary caudal fin is 

 marked off from the dorsal and anal fins by the presence on it of black 

 pigment. 



* The sexual organs only become visible at the superior part of the 

 abdominal cavity when the animal reaches the length of 20 cm. or 

 thereby. 



According to Robin, the civelles in the sea as in fresh water lose their 

 transparency when they arrive at the length of 6, 7, or 8 cm. ' At this 

 ' period they take on the yellowish brown tinge of the adult. From the 

 ' length of 9 cm. and better, 10 or 11 cm., they retain the preceding 

 ' colour. They are then opaque, being with difficulty examined by trans- 

 ' mitted light. It has, except for its length, the external appearance of 

 ' the adult. These peculiarities are still more marked in individuals of 

 ' the length of 12, 13, or 14 cm. According to Valenciennes it is at this 

 ' period (April or May), three or four months after their being hatched, 

 1 that they receive the name of civelle. At this period, according to this 

 ' author, they would be of a beautiful sulphur yellow colour.' From 

 observations made on elvers here, it seems probable that the appearance 

 of pigment is not solely dependent on the length of the eel. Some fully 

 pigmented young eels were found to be much smaller than others which 

 were still quite transparent. Transparent elvers, measuring from 63-75 

 mm., were procured in the neighbourhood of St Andrews in April 1895. 

 A dark coloured eel, 66 mm. in length, was found among the rocks in 

 a pool near a spring. The latter was quite opaque, in. colour exactly 

 resembling an adult. The head and dorsum were covered with stellate 

 black pigment corpuscles on a brownish-yellow ground ; the belly was 

 light coloured. Different stages of pigmentation were noticed in certain 

 transparent elvers. One little eel, measuring 67*5 mm., procured from 

 a salt water pool, had black pigment corpuscles laid down in certain 

 definite areas. Round pigment spots were present on the snout. On the 

 top of the head were two patches of large pigment corpuscles, one on 

 each side. A beautiful green coloration was present over the dorsal 

 half of the body. Beginning just behind the head where it was most 

 intense the colour grew fainter as it neared the tail. Black pigment 

 corpuscles were also present over the whole extent of the dorsum. Four 

 transparent eels from the Eden exhibited different stages in pigmentation. 

 They were captured on April 16th and were kept in fresh water in the 

 Laboratory until May 14th when they were examined. They all had 

 black pigment on the snout, head, dorsum and superior portions of the 

 sides. The green coloration described above was present. The two 

 patches of black pigment corpuscles on the head had united to form a 

 heart-shaped area. The pigment on the dorsum was more marked than 

 in the eel mentioned above. The pigment on the sides was continuous 

 in one specimen,' 68 mm. long; in the remaining three, 63, 68, and 73 



* Robin. Loc. cit. 



