34 DR. J. MURIE ON IRREGULARITY (Jan. 13, 
was run off, when three good-sized Salmon were found to have sur- 
vived ; these were bright, lively, and healthy, but ill-grown. One 
of these specimens sent to London weighed 15 oz., measured 144 
inches in its greatest length, and had a girth of 63 inches. The 
head was 3% inches from the snout to the extremity of the oper- 
culum, and appeared large enough for a 5-lb. fish. 
It is greatly to be regretted one of these three unusually interest- 
ing specimens was not preserved in spirits and forwarded to the 
British Museum. 
6. Lastly, I shall advert to an account, by Mr. Frank Buckland, 
of a ‘Salmon that had never seen the sea’”’*. This specimen was 
obtained from the river Wye in 1862, in the Parr condition, and 
transferred to a pond through which a streamlet of water ran. Four 
years afterwards it was taken out as a Salmon 11 inches long. 
IV. Irregularity of growth.—The life-history of Salmo salar, as 
all admit, is a most extraordinary one. The exceeding rapidity of 
their growth between their descent to and return from the sea is 
marvellous. But there are still two points as remarkable, viz. that 
a retardation of development is far from uncommon; and, on the 
other hand, causes occasionally ensue seeming as it were to stimu- 
late and quicken the usual accession of growth. Since Shaw’s ex- 
periments on the growth of Salmon-fry +, other observers have 
noted, and, in fact, it is now universally known to all those practically 
conversant with artificial Salmon-culture, that of the first year’s 
Smolts only some migrate seawards, while many of them remain 
behind in the fresh water. In the second year it also occasionally 
happens that in some fish no desire of migration ensues; but the 
accession of migratory instinct takes place in the ensuing season, or 
even later. In other words, some Smolts ripen earlier than others, 
and those remaining behind, which are slower in their seasonal mi- 
gratory instinct, remain apparently stationary as to growth. The 
cause of the retardation of the migratory stimulus, so far as I am 
aware, has not been satisfactorily accounted for; but clear evidence 
exists that the young self-detained Salmon are little or no larger . 
than their brethren a year or two younger. Their development is 
more or less retarded for the time being—but not necessarily con- 
tinuously so; for as soon as migration occurs, the usual growth 
concomitant with a sea-water visit takes place. Here, then, we have, 
from natural causes, retention and arrest of growth of young Salmon 
in a comparatively healthy condition in fresh water for two years or 
more. If such a fact or premise be granted, it seems to follow, as 
a necessary consequence, that if Salmon arrived at the Parr condition 
be prevented from migrating, they either remain stunted or increase 
in magnitude in a very diminutive ratio compared with their fellows 
that have spent a season in the sea-water. 
Regarding increase of size generally, and also unusual accretion 
of growth, in Salmonoids, this, as most authorities agree, is greatly, 
if not entirely, dependent on the abundance or scarcity of food, 
* Figured and described in ‘Land and Water,’ vol. i. June 2, 1866. 
t Trans. Roy. Soc. Edinb. vol. xiy. ke. 
