69 
Mr. Edmund T. Higgins, who had kindly come from Loudon on 
purpose, then delivered an address upon Otoliths. 
Remarking that his subject was essentially dry, except to a comparative 
anatomist, he referred to his thirteen years work upon the subject, and stated 
that his chief object that evening was to explain certain modifications in his views 
upon it, which had been brought about by a recent visit to the West Indies, 
because he considered himself indirectly responsible for views which had been 
previously advanced in that room. He was now enabled to state that these ear- 
stones had not only a distinctive specific character, but, contrary to fornier 
opinions, special generic characters also, and further, he believed that their 
microscopic structure would be found to be characteristic of groups. This was 
very important geologically, enabling species to be identified, and while many of 
the otoliths found in comparatively recent strata were identical with those of re- 
cent fish, a large anumber of those that occurred much lower down in the series, 
were identical with those of fish now existing in the tropical seas. 
Mr. Higgins then sketched the auditory apparatus of Reptiles, Birds, and 
Mammals, and minutely described that of Fish. In this class, from the difference 
of the medium inhabited, a very different arrangement was necessary. Except in 
the first family of Percidse, and in some of the Sharks and Rays, there was no 
vestige of any external ear or opening, the organs of hearing being hermetically 
sealed in the interior of the skull. They consisted essentially of three semi- 
circular canals, posterior, anterior, and external, and one vestibular sac, (seldom 
two, as frequently represented) communicating with each other in many and 
various modes. At several of the points of junction, enlargements (ampullae) 
existed, containing the two smaller otoliths, while the large characteristic one was 
always found in the vestibular sac. The smaller otoliths had the power of 
motion through the canals, and were only absent in the lowest order ; and while the 
canals themselves in the bony fishes were covered with cartilage, those of the 
cartilaginous fishes passed through the very substance of the skull itself. 
Professor Muller had pointed out that three substances were concerned in trans- 
mitting sound to the auditory nerve of the fish, viz., water — the solid parts of the 
body — and the fluid of the labyrinth ; but the speaker considered that a fourth, 
the air-bladder, ought to be added. In the families of Cyprinidse and Siluridai 
especially, the otoliths formed a chain below the vestibular sac, where was a 
connection with a chain of bones behind the skull, and thence again with the air- 
bladder. The last named bones were probably the true representatives of the ear- 
bones of Mammals, as it was satisfactorily proved that these otoliths were neither 
the analogues nor the homologues of the 4 Ossicula auditus ' in Mammals, as they 
did not occupy the same position in the skull, the true ear-bones never being 
found, as these always were, in the vestibular sac or its connected canals. The 
speaker regarded these otoliths as an excessive developement of the c otocone ' of 
mammalian ears. 
Mr. Higgins then described the otoliths more minutely. They were composed 
of carbonate of lime and phosphate of lime with a little animal matter, and it was 
