PROCEEDINGS OF THE SOCIETY. 137 
The Porbeagle Shark seems to hunt for food in small packs of 
three or four—possibly the parents accompanied by their young, 
which may not amount in number to more than two. In the 
summer of 1889, a young shark of this species, nearly 3 feet in 
length, was caught in a net off Carradale. It had been accom- 
_ panied by two large sharks which had escaped by tearing the 
nets. It appeared to have been about three or four months old, 
_ and had two rows of small teeth. Its age, if correctly guessed, 
would indicate that the Porbeagle Shark brings forth its young 
in May or June. According to Pennant, the female fish gives 
_ birth to two young ones annually, and the two-horned uterus 
contains quite space enough in each division for a young shark. 
The paper was illustrated by means of preparations, diagrams, 
and a photograph of the Loch Long sharks. 
Professor Prince read a paper on the Comparative Anatomy of 
the Organs of Hearing. He stated that in most diverse animals 
these organs conform to one type. In Ceelenterates (like the 
Meduse, Ctenophora, &c.) a simple sac with a lining of sensory 
cells and projecting hairs, and usually a central otolith, forms the 
auditory structure, which is either seated at the aboral pole, as in 
Beroe or Cydippe, or in a series around the margin of the bell, as 
in certain Discophora. In the Worms and Mollusks similar 
organs are present; in the latter these are usually situated near 
the pedal ganglion, but always innervated from the cerebral ganglia. 
The Crustacea and Insecta possess slightly different auditory 
structures, placed, as in the lobster, at the base of the antennule 
and open to the external water, or, as in Mysis, situated on the 
tail. In the locust, the hearing organ is a hollow drum with two 
tympanic membranes on the tibie of certain of the walking legs. 
In the Vertebrates, we find the lowest types (like Myzxine and 
_ Petromyzon) having a pair of lymph-filled sacs with semicircular 
canals and an endolymphatic canal and sac; in higher Fishes— 
Sharks and Teleosteans—other parts are added, e.g., three semi- 
circular canals, ampulle, and a trace of a lagena, which latter, in 
_ still higher types, forms the complex cochlea. Branchial elements 
"come into connection with the ear in Birds and Mammals, the 
chain of ossicles being really derivatives from the mandibular 
and hyoid cartilages, the Eustachian tube and external opening 
representing the aborted visceral slit. 
I 
