178 
ZOOLOGICAL LITERATURE. 
propagate its species; males which are one or two years old are 
from 110 to 175 mm. long, and about one half of their number 
are sexually developed, whilst the other half are in an immature 
state. On the other hand, females of the same age, and from 156 
to 163 mm. long, are only exceptionally fertile, by far the greater 
part remaining sterile for a longer period ; in the sterile females 
the longest caudal rays are twice as long as the shortest, whilst 
in a mature female (163 mm. long) the longest caudal rays were 
21 mm. long, and the shortest 11 mm. ; and in another (156 mm. 
long) the longest rays were 23|mm., and the shortest 14 mm. 
The depth pf the incision of this fin remains relatively the same 
during the growth of the individual, until the period of the 
sexual development arrives. 
The same variations in the development may be observed in 
the migratory forms (in those which migrate to the sea, as well 
as in those which go into some large freshwater lake) and in 
the Salmon. However, fertile specimens of these forms have 
been found, in which the caudal fin was more deeply emarginate 
than usual, and vice versd. Some other specimens, from two to 
three years old, appeared to have remained in the rivers beyond 
the usual time! Sterile specimens of the Salmon cannot be 
externally distinguished from fertile ones of the same age. 
Towards the end of the paper the author makes some remarks 
on immature specimens of the Scandinavian Charr. He distin- 
guishes two forms of Charr — a larger one fr*om Lapland, Lake 
Wetter and other large lakes, and a smaller one from the smaller 
lakes of Jemtland, AVermland, SmMand and Norway; but he is 
inclined to regard them as modified forms of one and the same 
species, analogous to those of the Eiver-, Lake-, and Migratory 
Ti’out. 
The paper is accompanied by eight plates illustrative of the 
changes of the sexual organs and caudal fin. Entire figures of 
a male of a River-Ti’out and of a Migratory Trout are given on 
taf. 13. Fig. 1 of taf. 14 is said to represent a young fertile 
male of Salmo salary but we should never have recognized in it 
the British Salmo salar of the same age and sex. It is not im- 
possible that British and Continental naturalists may treat of 
very different fishes, although they use the same names. 
Hr.’ Malmgren has examined the Salmonoids of Finland, 
entertaining the same opinion as Mag. Widegren with regard 
to the specific identity of the different European Salmonoids; 
but he considers it improper to refer these varieties to one 
species, without taking due notice of, and recording, the differ- 
ent forms occurring in nature*. Thus, what has been called a 
* It would liave been very proper if Hr. Malnigreii had been guided by 
the same principle in his notes on Charr (Wiegm. Arch. 1804, p. 031). 
