In the foetus of the Dolphin, according to Miller, the lobules of the kidney consist principally of convoluted uriniferous ducts, extending from the apex to the circumference of the lobule ; the iotertwinings of the tubuli are greatest in the intercortical portion. It is a curious fact, Professor Owen remarks, that the supra-renal gland in the Porpesso presents a certain resemblance to the kidney in its lobulated exterior ; but, he adds, the analogy extends no farther, for on making a section of this part it was found to consist of the usual continuous compact substance.
Generative System.—John Hunter remarks that the organs of genera tion of this order of animals come in both sexes nearer in form to those of the Ruminants than of any others ; and this similarity is particu larly remarkable in the female ; in the male their situation varies on account of the modification of the external form of the body.
The female organs in the Rytina have been described by Steller ; and Sir Everard Home has given an account of those of the Dugong. (' Phil. Trans.,' 1820.) llunter, in his paper on Whales has entered particularly into the structure of those of the Zoophagous Cetaceans. The period of uterine gestation does not appear to be certainly known ; the number of young is generally considered not to exceed one, there being but two nipples ; the glands for the secretion of milk are two, one on each aide of the menial line of the belly at its lower part. The milk is very rich, like that of a cow to which cream has been added.
Professor Owen remarks, that much stress has been recently laid on the supposed existence which the muscles surrounding the mam mary gland afford in the act of suckling, by compressing the gland and ejaculating the milk accumulated in the dilated receptacle or reservoir ; but he observes that, considering how great the pressure of the surrounding water must be upon the extended surface of the mam mary gland, it may readily be conceived, that when the nipple is grasped by the mouth of the young, and the pressure removed from it by the retraction of the tongue, the milk will be expelled in a copious stream by means of the surrounding pressure alone, indepen dently of muscular aid. The Professor adds, that the intimate struc ture of the mammary gland in the Zoophagous Cetacea is essentially the same as in the Ornithorhynchua, being composed of an innumerable quantity of meal tubes ; these are however shorter than in the Ornithorhynchus, and their glandular parietes are firmer ; they are well shown in the figure of the mammary gland in a young Piked Whale (Balamoptera rostrata) given by Miller in his seventeenth plate, fig. 2., and according to that author present, after the Ornithorhynch us,
the simplest structure of the mammary gland in the entire mammi ferous series of animals.
Brain, Nervous System, and Senses.—The brain is well formed. In the Porpesse and the common Dolphin it has been stated to be as highly developed as in any mammiferous quadruped. In the greater whales there is reason for supposing that the ratio of the weight of the brain to that of the body is In the smaller Cetaceans it is not diminished to a proportionate size, as its extraordinary development in the Dolphin testifies.
SmelL—Hunter observes that in many of the Whale Tribe there is no organ of smell at all, and in those which have such an organ, it is not that of a fish, therefore probably not calculated to smell water. It becomes difficult therefore, he remarks, to account for the manner in which such animals smell the water ; and why the others should not have had such an organ, which seems to be peculiar to the large and small Whalebone Whales (Balawa mysticetus and Balamoptera rostrata); the organ, in those which have it, he adds, is extremely small, when compared with that of other animals, as well as the nerve which is to receive the impression.
Taste.—The complicated and indeed delicate structure of the tongue in the Phytophagous Cetaceans indicates that they must enjoy the sense of taste, although the tongue is capable of but slight motion.
But it has been doubted whether the Zoophagous Cetaceans are endowed with a special organ for the enjoyment of this sense. No fossulate nor conical papillae are present in the tongue of the Dolphin or of the • slight elevations, the middle of which appears to be perforated, are Only perceptible, and the fringed edges would seem to lead to the notion that their object is more intended for furthering the sensations of touch.