_Brain and Nervous System._--The erectile tissue surrounding the spinal cord and origin of the spinal nerves in the Cetacea did not extend into the interior of the cranium. The entire encephalic mass weighed 2-1/2 lbs.: cerebrum, 2 lbs.; cerebellum, 1/4; pons and medulla, 1/4 = 2-1/2. Compared with a drawing of Camper of the _Delphinus Phocaena_, the brain was found to differ remarkably, in being much broader in the line of the middle and posterior lobes. In no animal did I ever find the fibrous structure of the brain so well marked; and this extended to the cerebellum[D]. I give here some measurements of the brain, which may be of use to future observers. The brain is short from before backwards, but broad transversely:-- Antero-posterior diameter 5-2/8 inches. Breadth 8 inches. Greatest breadth of the cerebellum 4 inches. Length of the cerebellar hemisphere 4-6/8 inches. Depth of ditto 3-2/8 inches. Weight of the encephalic mass 2-1/2 lbs. Depth of the interhemispherical fissure 1-2/8 inches. Length of the corpus callosum 1-7/8 inches. Weight of cerebrum 2 } Weight of cerebellum 0-1/4} = 2-1/2 lbs. Weight of the pons and med. oblongata 0-1/4} _Nerves._--The 7th pair was found to be unexpectedly large and firm, including both portions. The anterior roots of the spinal nerves were far more numerous than the posterior or dorsal. _Muscles._--The panniculus carnosus, strong and fleshy, extended nearly over the whole trunk. The recti abdominis were powerful, and attached inferiorly in this way:--A portion runs to the pelvic bones; a much stronger to a strong aponeurosis, situated between the anus and the root of the tail. The erector muscles of the spine (sacrolumbalis, longissimus dorsi and multifidus spinae) weighed fully 16 lbs. They had but slender costal attachments; but their spinal (small delicate tendons) were innumerable. The scaleni were very large; and the vessels held the same relation to them as in man. The serratus magnus was comparatively small. The larger rhomboid had no spinal attachment; the minor rhomboid seemed to be the larger of the two. The pectorals were comparatively small. The adipose tissue appeared to be wholly confined to the subcutaneous region. The muscles were of a deep brown colour, full of blood, with a short, dark, and well-flavoured fibre: when cooked, they had a strong resemblance in flavour and taste to the flesh of the hare. Part II. THE BALAENA WHALES, OR WHALES WITH WHALEBONE.