324 
THE FAMILY OF EELS. 
very long time after the influence of the pulmonic heart is 
entirely removed. The vessels which issue from the caudal 
heart appear to have a particular distribution to the spinal 
marrow;” but it is evident from the figure that the current of 
blood is directed to, and not from the orifice or outlet forward 
from the caudal heart; so that these smaller vessels collect the 
blood into this organ, and do not distribute it. 
Another remarkable organization in this genus, or at least 
in the Eel and Conger, but of which the use is as yet unknown, 
is described by the Rev. W. Houghton, F.L.S., in the “Journal 
of Microscopical Science,” with a plate, vol. iv, N.S., but which 
requires further investigation. He remarks that having been 
occupied at intervals in dissecting a number of Eels and a 
couple of Congers, he observed the invariable presence of 
two subtriangular openings in the fleshy portion of the head, 
just at its juncture with the spinal column. His first impression 
in regard to the use of these orifices was that they were 
connected with the auditory organs; but, he adds, although 
Mr. Cholmondeley Pennell, in his work, “The Angler Natur- 
alist,” asserts the presence of an ear or auditory aperture 
amongst the mucous pores about the head, from the most 
minute examination of a large number of the heads of Eels, 
he confidently affirms that no such auditory aperture exists. 
Upon inserting a bristle in each of the orifices above 
referred to, and clearing away the flesh, each bristle was found 
to have traversed a closed-in tube in the skull, and to have 
come out just above the bone of the orbit; but on close 
observation they were found to have no connection with the 
organ of hearing. These tubes are very slender, and each one 
of them terminates in a membranous fold in the tissue just 
beneath the skin, above the eye; which fold contains a thin 
fluid, that does not bear any resemblance to mucus. It may 
have some connection with the habits or faculties of these fish, 
that the whole of the optic nerve does not proceed to be 
joined to the optic lobe of the brain; but that portion of it 
which passes to another part of the brain must be connected 
with some other function besides that of discerning outward 
objects. 
It is a character of this family to have also an air-bladder 
of 'considerable size ; at the middle of which is what may be 
