SALMONIM]. 57 



tamely gives in, while at table it is muddy and coarse, like an English tench. 

 Perhaps were its digestion more rapid its vigour would increase and it seems as if 

 nature is now augmenting the number of its ccecal appendages, and consequently 

 increasing the extent of its intestinal area. As regards the Loch Leven trout, 

 reasons exist for suspecting the race to be more nearly allied to the anadromous 

 than to the true fresh water species. We may thus be dealing with a race that is 

 changing from a marine to a fresh water form, living as it now does in fresh water, 

 but having the colour of a sea-trout. Some examples in the British Museum, 

 captured during the month of April, have the ccecal appendages fewer in number 

 than commonly perceived in the Sahno levenensis, but they are wider than normal, 

 and may be instances of a confluence of two or more into one, but it is suggestive 

 that this character is very inconstant in this species, which seems to be in a 

 transitional condition ; perhaps their diameter will gradually diminish, until in 

 time cceca similar to such as are found in the common brook-trout will be present. 

 Whatever the result of such an investigation might be, it is still evident that 

 the number of ccecal appendages in the various species of trout or salmon is 

 inconstant, and consequently should be most guardedly employed for the purpose of 

 constituting a species. British marine salmonidse possess more of these appendages 

 than do the strictly fresh water forms, while a change of climate to the antipodes 

 seems to increase the necessity for these organs, and as a result in their numbers, 

 in such as are bred there. 



Here I shall refer to one of the so-called inconstant variations, or changes of 

 colour, such being closely relating to the foregoing remarks upon the Loch Leven 

 trout, the tints of which resemble those of sea forms as much as do the number of 

 their ccecal appendages. 



Variations in colour must be due to some cause acting directly or indirectly on 



the fish. Thus, among the young of the members of the Salmonidce, we perceive 



that dark bands or bars down their sides are almost universal, being evidently 



hereditary throughout the family. This same banding of the young is seen in 



some of the horse-mackerel, Caranx, flying-fish, Exoeoetus, the gar-fish, Belone, 



etc. It has been erroneously asserted that the young of the migratory forms of 



salmon and trout possess two or three more bars than the non-migratory brook 



trout. These bars, as well as the black and red spots on the sides, are almost 



invariably lost in the anadromous forms when they are in a condition to migrate 



into salt water, and assume their silvery smolfc stage (with or without X-shaped 



black spots). In rivers it is rare for bands to be retained in adult trout, while 



most of the black and red ocellated spots as a rule remain, although instances 



have been recorded in which they have entirely disappeared. In streams where, 



due to some local cause, the trout are small, it is not uncommon to perceive the 



bars as well as the black and red ocellated spots retained throughout life. I 



found this obtained among some from brooks near Penzance ; in fact, they were 



as brilliant as young parrs, to which, except for the white edging to some of their 



fins, they bore rather a striking resemblance : in a few instances I have also 



observed this, but to a much fainter degree, in trout taken at Colesbourne, in 



Gloucestershire. Examples of brook trout have been found on emigrating to the 



sea, as a rule (to which there are exceptions), to assume the brilliant silvery 



livery of the migrating salmonoids, as well as their X-shaped black spots. Mr. 



Harvie Brown remarked (June 12th, 1882) on having caught at Durness several 



so-called " sea trout " from a sea pool, or first pool at the mouth of the river, fresh 



water at low tide, salt or brackish at high tides. From their silvery appearance 



they are known as " sea trout," but are the river form acclimatized to brackish 



or nearly salt water, or else periodically visiting the same between tides. 



Mr. Lockington (American Naturalist, May, 1880, p. 368) observed the same 



phenomenon in the Western hemisphere, where the Sahno iridens, a resident in all 



Calif ornian brooks and rivers, descends in the autumn to the sea, and when in 



salt water changes its colour to a steel blue, while its spots mostly disappear. 



But although we may generally anticipate the non-migi-atory forms to be more 

 vividly coloured than such as are strictly marine, still among the former there are 

 numerous variations in tints and markings which have been explained in more 



