— 242 — 



paid to the possible differences between males and females, nor is it stated whether the 

 specimens were yellow or silver eels. 



New investigations were therefore necessary in order to obtain a true basis for con- 

 clusions, and I carried out these in connection with the counting of the vertebrae. For 

 the comparison only female eels of over 50 cm. in length were used. To determine first 

 of all whether any difference could be detected according to age, 45 yellow female eels 

 varying in length from 46 to 73'5 cm. were examined on the market at Copenhagen. 

 This examination showed that no difference could be detected between the smaller and 

 larger specimens in the position of the dorsal and anal fins. 



Next, 40 silver female eels were examined on the market at Copenhagen'. The 

 length of these varied from 50'5— 67-5 cm., and it was found that no apparent difference 

 occurred between the yellow and silver female eels of the same size (total length) in 

 regard to the position of the dorsal and anal fins. 



The American eels measured for comparison were in the frozen condition and they 

 were measured after being thawed up. The position of the fins was measured in 56 spe- 

 cimens in a.11 (yellow and a few half-silver female eels), varying in length from 55'5— 79 cm. 



The feature which best shows the difference between the American and European 

 (Danish) eels is the distance from the beginning of the dorsal fin to the 

 beginning of the anal fin expressed in % of the total length (measured 

 from tip of snout to end of tail). The following comparison shows the result of the 

 measurements : 



Angziilla chrysypa (Canada) Anguilla vulgaris (Denmark) 



■ Yellow r> /T- . 1 r »u c \ Yellow Q (Total length Silver 9 (Total length 



, ^ , ,r -I \ 9 (Total length so"? — 67'5 cm.) * ^ , " . \ . ^ 



(a few half silvery) '^ ^ o d :> / 3 / ^^_^y^ (-„.,_^ jq.j_6^.j cm.) 



9'i % io'8 % 107 % 



(average of 56 measurements) ^j. ^^ ^^J^^^fements) of 40 mJasurements) 



The result of the investigation ^ is that I am able to confirm Meek's statement that 

 the distance from the beginning of the dorsal fin to that of the anal estimated in per- 

 centage of the total length is on an average less in the American than in the European 

 eel (average respectively 9'l % and lo-8%). The reason for this essentially is that the 

 dorsal fin begins further back in A. chrysypa than in A. vulgaris, whereas there 

 is less difference in the position of the anus. 



It should be mentioned further, that the position of the dorsal fin may undergo 

 remarkably great individual variation. In 2 Danish eels of 60 cm. in length, 

 for example, I found the distance from the tip of the snout to the beginning of the dorsal 



1 All the Danish eels were measured by Cand. A. Strubberg, the American eels by both of us conjointly. 



2 Measurements based on the dimensions of the head do not serve jprobably for separation (as Meek's 

 measurements also show), the form of the head changing so much during the development of the eel. Therefore 

 the characters given by Jordan & EvERMANN (Fishes of North & Middle America, I, p. 34.7, 1896) as distinguishing 

 the two species, cannot all be credited with great importance, as no special comparison of silver (or yellow) 

 eels from America has been made with silver (or yellow) eels from Europe. The following distinguishing 

 characters are given: (a) Distance between'origin of dorsal and vent s/e to 11/4 in head; pectoral 3 to 3^/3 in 

 head; head 21/2 to 24/5 in trunk; upper jaw 33/4 to 41/4 in head. Yellow, brown or black, underparts paler 

 , . . Ang. vulgaris, (b) Distance between origin of dorsal and vent I'/e to 2 in head; pectoral 25/6 to 3^/5 in 

 head ; head 2 to 21/2 in trunk ; body more robust and trunk slightly shorter than in A. vulgaris, otherwise 

 similar . . . Ang. chrysypa. 



