of the Fishery Board for Scotland. 9 
has an important bearing on several problems connected with sea 
fisheries. 
One method by which the growth and age of fishes is determined 
is by the tabulation of the measurements of large numbers taken 
at the same time and place. From the fact that the spawning 
season of a species, and, therefore, the rate at which a new genera- 
tion makes its appearance, is usually limited to a few months of the 
year, the range of the sizes and the average size of the different 
generations or annual series differ from one another. By the 
tabulation of large numbers of measurements it is thus possible to 
distinguish different generations and to assign the range of size 
and the age of the fishes belonging to them. With the earlier 
generations this method is in most cases quite satisfactory, but 
owing to the very different rate at which members of the same 
generation grow, the larger of an earlier generation overtaking and 
exceeding in size the smaller members of the next older generation 
—a process which increases with age—it becomes difficult or im- 
possible to separate the older generations from one another by this 
method. 
Another method that has of late been largely adopted consists in 
determining the number of the zones or lines of growth in certain 
of the hard parts of the body. Fishes do not grow continuously 
throughout the year, their growth exhibiting a usually well- 
marked periodicity in relation to the changes of the temperature of 
the water, being as a rule, and in most places, rapid in summer and 
slow in winter. This periodicity is indicated by lines or zones on 
some of the skeletal structures, notably on the ear-bones, or 
otoliths, the scales, and certain bones of the skeleton, the structure 
which shows them best varying somewhat in different species. By 
counting the lines or zones it is thus possible to tell the age of a 
fish, just as by a similar method, and for a like reason, the age of a 
tree may be discovered by the number of rings present in a section 
of the trunk. 
To the present report Mr. J. T. Cunningham contributes a paper 
on this subject, dealing specially with the plaice and the cod. He 
describes the structure and formation of the ear-bones and scales, 
and the mode in which the lines or zones are produced. One of the 
chief objects of the observations was to test the question how far 
the lines of growth in the skeletal structures of fishes were trust- 
worthy indications of age—whether the annual increments of 
growth or deposit could be definitely distinguished and counted in 
all cases. He shows that it is often necessary to test the indica- 
tions of one structure by an examination of the others, though in 
many instances the age of the fish may be well determined by the 
examination of one of them alone. 
The result in regard to the two species mentioned is to show 
generally that they do not grow so fast or reach maturity so soon 
as is commonly supposed. It was found that cod at two years of 
age measure from ten to thirteen or fourteen inches in length, at 
three years from seventeen to nineteen, and at four years about 
twenty-seven inches, so that they would spawn as a rule in their 
fifth year. Plaice from two-and-a-half to about four inches were 
one year old, from about four to six-and-a-half inches they were 
two years old, while those at three years measured up to 12 inches, 
