n. The
enormous Cachalot, with its vast teeth implanted only in one jaw, is
generally understood to prey chiefly on the Cuttlefish. The food of the
true Whale, or _Mysticetus_, is well known to be the Clio and other
smaller Mollusca, with which certain regions of the ocean abound; the
same, or similar, is probably the food of the more active and restless
Rorquals, found in both hemispheres. The Dolphins, or Toothed Whales,
generally prey, no doubt, on fishes of various kinds; yet, even as
regards these, it has been proved by my esteemed friend, the late Mr.
Henry Goodsir, that some of the largest, following in the wake of the
herring shoals, prey not on these, but on the various microscopic food
(the Entomostraca and other marine animals) which I was the first to
prove to be the natural food of many excellent gregarious freshwater
fish, as the Vendace, Early Loch Leven Trout, the Brown Trout of the
Highland and Scottish lakes generally, and of the Herring itself[F]. It
is scarcely necessary to add, that the complex apparatus connected with
the exterior nostrils of the Dolphins is wholly wanting in the Balaena
Whales,--a fact of which M. Cuvier was not aware when he wrote his
celebrated Treatise on Comparative Anatomy.

_Appendix_.--Since writing the above, I have received an answer to a
letter I addressed to my friend, John Goodsir, Esq., Professor of
Anatomy in the University of Edinburgh. The request contained in my
letter to Mr. Goodsir was, to examine for me the skeleton of a foetal
_Mysticetus_ now in the University Museum. The foetus from which this
skeleton was prepared was removed from the uterus of the mother, killed
in the North Seas by the seamen of a whaling ship, by one of my former
students, Mr. R. Auld, who presented the specimen to me. The point at
issue was the composition of the cervical vertebrae in the true or
Greenland Whale, the _Balaena Mysticetus_. M. Van Beneden, to whose
memoir I have referred in the commencement of this, says, on the
authority of Eschricht, that at no age whatever do we find in true
Whales (meaning, I presume, the _Mysticetus borealis_ and _australis_)
any distinct vertebrae in the cervical region, as in other mammals. A
fusion of all into one bone or cartilage seems to take place even in the
youngest foetus. Now, I had enjoyed the rare opportunity of dissecting
the foetus of the _Mysticetus_, and I knew that the skeleton, prepared
with the greatest care, was still preserved i