gantic Arctic Rorqual, the largest, perhaps, of
all living beings. Certain of the details have been from time to time
laid before the public, but in an extremely scattered and incomplete
form, and without the illustrations (artistic), which explain so much
better than any verbal description. The greater part is still before me
in manuscript. It is my intention in the following contributions to
endeavour to connect them together, adding to those already published
many facts I find in MSS. The original drawings, made by my brother and
by Messrs. Edward Forbes and Henry Goodsir (who were at that time my
students and assistants), are still in my possession.

_Determination of Species._--The determination of species as regards the
_Cetacea_ is one of much difficulty; Cuvier met this difficulty by an
appeal to anatomy. The number of vertebrae composing the vertebral column
(exclusive of the cephalic) seemed to me a tolerably secure guide in the
determination of species,--being aware, however, that some doubted the
method, believing that the number of the vertebrae might vary, first,
with the individual, secondly with the age of the specimen. I still
continue to be of my original opinion, that the number of vertebrae
comprising the vertebral column, properly so called, may safely be
trusted in determining the species of the Cetacea; and with this view I
drew up the following Table, excepting from it the genus _Dugong_, which
I have never considered to be a Cetacean:--

_Tabular View of the Number of the Vertebrae in certain Cetacea._

(Cephalic vertebrae excluded.)

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| Authorities. |
| ---------------------------------------------------
| SPECIES. | CUVIER. RUDOLPHI. KNOX. J. HUNTER. HUNTER |
| | (Glasgow.)|
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| | | | | | |
|1. MYSTICETUS. | | | | | |
|Skeleton of the | | | | | |
|foetus (the | | | | | |
|cervical reckoned| | | | | |
|as 7) of the | | | | | |
|_Mysticetus_ | |