of the Fishery Board for Scotland. 



49 



already known might be useful as a means whereby we could ascertain 

 what was the species of fish that those found in the stomachs belonged 

 to. 



Of course, the usefulness of the earstones for this purpose depends on 

 whether the difference between those of one species of fish and those of 

 another is sufficiently distinct and constant, either in their size, form, or 

 sculpture. This information, however, could only be acquired by the 

 comparative examination of the earstones of many kinds of fishes and 

 also of large and small examples of the same kinds. Unfortunately, I 

 have not been able to give so much attention to this research as it 

 deserved, nevertheless a good deal of time has been devoted to it, and 

 though the results have been in some respects disappointing, several 

 interesting facts have emerged which will be referred to presently. 



The earstones of about seventy species of fish are described in the 

 sequel and, with one or two exceptions, the descriptions are illustrated 

 by enlarged photographs. Before proceeding, however, to describe 

 the various forms, the following remarks may not be out of place, and 

 the first thing I wish to refer to is the position of the earstones. 



The earstones or otoliths of teleostean fishes are contained within 

 special chambers — the ear-chambers — one on each side of the head and 

 situated between the eye and the base of the skull. There are usually 

 several stones in each chamber, one being comparatively large and the 

 others very small. The form of the large stone is generally well defined, 

 but the others are irregular in shape, and therefore, in this paper, the 

 term earstone or otolith will refer only to the large stone. The otoliths 

 are not outgrowths from adjoining parts of the skull, but are free within 

 the ear cavity, and are covered by a thin membrane to which nerves are 

 attached. 



I have endeavoured to ascertain whether the size of the earstones was 

 in any way correlated with the intensity of the sense of hearing, that is, 

 whether the possession of large or small earstones was an indication of a 

 higher or lower development of the sense of hearing, but have been 

 unable to obtain any positive evidence bearing on this question. For 

 example, haddock, coal-fish (especially in the earlier stages), lythe, and 

 also cod have their sense of hearing tolerably acute. This was demon- 

 strated over and over again at the Rothesay Aquarium, and these fish 

 have large earstones. The conger, on the other hand, which has com- 

 paratively small earstones, appears to be a dull and listless fish. But it 

 has been noticed that lumpsuckers, and more especially the young of that 

 species, have a keenly intelligent look, yet their earstones are extremely 

 small compared with the size of the fish. 



The position which the earstones in situ occupy in relation to the head 

 of the fish has been observed in a number of cases, and is referred to in 

 the descriptive part of the paper. It may be stated here, however, that 

 in the majority of species where careful observation could be made, it 

 was observed that the two earstones were placed lengthways, or nearly so, 

 with the head. They were not, however, usually parallel to each other, 

 but diverged more or less posteriorly. In the case of many of the larger 

 fishes — except the Pleuronectidse — the earstones are elongated, and have 

 one end truncated, often obliquely, and the other end angular or produced 

 to a more or less sharp point, as is well exemplified by those of the 

 whiting. The truncated end is usually directed towards the front of the 

 head, but there are a few fishes, such as the herring and some others, 

 where the anterior end is pointed. It may also be remarked that the 

 earstones in these larger fishes have frequently one side concave and the 

 other convex. The convex sides usually face each other, and are com- 



