ol Part I1I.—Twenty-fourth Annual Report 
The megrim or whiff is the only kind of fish I have met with that 
exhibits a fairly constant difference in the shape of the right and leit 
earstones. At first I imagined this difference to be merely accidental, 
but the examination of several specimens, both large and small, revealed 
similar differences in all of them. 
The earstones of the argentine have also a peculiar shape, and are 
unlike any of those that have been examined. They may be described as 
scaphoid or boat-shaped, except that the length and depth are nearly the 
same. Two pairs of these earstones are represented on pl. i. B., figs. 44 
and 45, and photographs of them considerably enlarged will be found on 
piay., ug. 9: ; 
The earstones of very young and immature fishes may, but frequently 
do not, possess the characters peculiar to the species as seen in the adult 
form, and it is this fact that makes the identification of fishes by the 
earstones alone unsatisfactory, whereas if the fishes be of adult size, or 
nearly so, the uncertainty of determination is greatly minimised. There 
can, for example, be little or no difficulty in recognising the earstones of 
adult whiting or codfish or of those of the hake. 
Besides the difference in the shape of the earstones of fishes there is 
also. sometimes considerable differences observed in the proportional sizes 
of those of different fishes—that is, it does not always follow that a large 
fish belonging to one species will have earstones proportionally larger 
than a smaller fish belonging to another species, for we sometimes find 
that the difference is the other way. For example, the earstones of a 
lumpsucker fifteen and a half inches long measured 1‘5mm. by 1*3mm.; 
a lemon dab twelve inches long had earstones that measured 3‘Omm. by 
2mm., while those of a long rough dab ten inches long, or only two-thirds 
the length of the lumpsucker, measured 6mm. by about 4°5mm—four 
times the size of those of the lumpsucker. Then, again, a catfish, the 
length of which was twenty-seven inches, possessed earstones 4mm. long ° 
by 2°5mm, at the widest part, while a hake of about the same length as 
the catfish was found to have earstones nearly 25mm. long by about 9mm. 
at the widest part. Jn further contrast with the earstones of the fishes 
just mentioned, it may be stated that a codfish measuring fully three feet 
in length had earstones of about the same width as those of the hake, but 
they were nearly 7mm. shorter, their length reaching only to 18mm., but 
the difference in length was fully made up by their more massive struc- 
ture. The weight of these two earstones was about 22 English grains, or, 
more correctly, 1:485 grammes, while the weight of the two otoliths from 
the hake was about 12 English grains, or ‘735 grammes. It may also be 
mentioned that the two earstones of a codfish which measured forty inches 
in length weighed nearly 30 English grains—and it should be noted that 
this was the weight of them after they had been thoroughly dried. 
Moreover, the earstones of teleostean fishes appear to consist almost 
entirely of calcareous matter, for when those from a tolerably large codfish 
were subjected tu a red heat they remained practically unaltered in size or in 
shape, but were so brittle that they were easily crushed between the finger 
and thumb. On the other hand, when otoliths were placed in dilute 
hydrochloric acid they completely dissolved away with much effervescence, 
leaving but the merest trace of organic matter. 
This calcareous matter does not form a homogeneous mass, but is 
deposited in layers, and the density of each alternate layer is usually less 
or greater than the one immediately preceding. In some cases these 
layers are arranged so regularly as to imply a more or less regular and 
periodic activity or quiescence in the secreting tissues by which the ear- 
stones are formed, The result of this alternating activity and quiescence 
