" From the examination I have been able to make of the baleen of Balanoptera rostrata, and of different manses of small blades of Balana a ustralis, it would appear as if there was, at least in these two species, two series of baleen on each side of the palate; the extenial series being formed of largo triangular blades placed at a certain distance apart; and the internal, in Balcenoptera rostrata, formed of smaller, much thinner, triangular pieces, placed much closer together, and forming a very dense screening apparatus; and in Balcena australis the inner series is formed of numerous separate narrow strips of whale bone, each ending in a pencil of hairs, which vary in size from that of small twine to that of tape, half an inch wide : these are placed behind the others, and gradually increase in size from the innermost to the broad external series.
"The baleen, or whalebone, affords good characters for the separation of this family into sections. Mr. Knox (' Cat. Prep. Whale,') gives the best account of the development, position, and distinction between the baleen of the whales of the North Sea which has come under my observation ; and it agrees with the observations I had made on the subject before I could procure his pamphlet.
"In Baena maximus, Knox ("palm' Antiquorum), 314 external or labial plates (baleen) were counted on each side. Towards each extremity these plates degenerate into bristles, and admit of being counted with difficulty. Towards the mesial line the baleen as a' mass diminishes gradually in depth, giving the whole palatine surface an elegant arched form. The 314 external or labial plates do not extend to the whole extent in a transverse direction, but a system of numerous small and narrow plates succeeds the external ones. For each external plate twelve (internal) smaller ones could be easily counted; so that the number of plates which could be counted, and not including the bristly terminations towards the snout, pharynx, and mesial line, stands thus: external or labial plates 314 ; internal small plates, corresponding to each external one, 12; total number of baleen plates 3768. The longest plate of baleen is placed about the centre of each of the sides, and measured 26 inches in length, and 15 inches in breadth. The substance when recent is highly elastic and very heavy : the whole weighed nearly two tone.
" It is short or long according to the species of whale, being modified entirely by the more or less arched form of the upper jaw. Mr. F. Knox first pointed out this curious and important fact. The usual conclusion come to by all persons was, that the size of the whale corresponded to the length of the bone or baleen. Now, this is only good with regard to one species of whale, and not at all to the whole group of Whalebone Whales. (Knox, Cat. Prep. Whale,' 8.) "In Balcena minimus, Knox (Balcenoptera rostrata), 307 external or labial (baleen) plates can bo counted on each side. Towards each extremity these plates degenerate into fine bristles, which were not counted. The platea hang perfectly- parallel with each other, and from their closeness and fringed lingual aspect must act as a very perfect filter in collecting the minute molluscous animals, and at the same time enable the whale to eject the water. The food of the whale is still a much disputed point. It is now generally admitted that the Mystiestus lives only on small. Medusa, shrimps, &c., but that the other species of Whalebone, Whale devour inconceivable quantities of fish ; for instance, M. Desmoulins states that '600 great
cod and an immensity (probably as many thousands) of pilchards have been found in the stomach of a single RorquaL' "Mr. F. Knox, in dissecting the Balcena maximus, saw no cavity in the course of the viscera which could have contained six cod of ordinary size; that of B. minima was empty, although the Frith of Forth, particularly at and above Queensferry, abounds at all seasons with herrings and other fishes and their fry. The want of teeth by no means renders it impossible that the Balcrna with baleen can live on largo fishes ; but the extreme narrowness of the gullet (that of B. maxims barely allowed the passage of the closed human hand, and that of B. minims,' was certainly narrower than that of an ordinary sized .cow), added to the want of teeth and the want of proper authenticated information on the subject, are strong arguments in favour of the hypothesis that they do not. (Knox, Cat. Prep. Whale,' 16.) "The thickness of the plate of baleen depends on the number of bristles. In the baleen of B. maxima there are 506 bristles in the thickness of the plate, and by a rude enumeration there appeared to be at least 130 bristles in each inch. The whole breadth of the plate being 5.1 inches gives us 747 bristles entering into its composition. These bristles are matted together to the extent of 11 inches on the external and 5 inches on the internal margins by a substance like minute laminte or scales, and which may be seen by the aid of a microscope to invest the free bristles at the fringed extremity of the plate. We have often observed the facility with which some baleen can be split up, and were struck with the fact that the baleen of B. ma.rimus would not split. The removal of the external lamina in the plate under description shows the cause of this : about 64 inches from the root of the plate, many of the bristles have deviated from their direct parallel inclination, and become intimately twisted and interwoven with each other. It has been attempted to prove the ago of the whale from an examination of the baleen, in the same manner as we judge of the age of cattle by certain annulated markings on the horns. On the plate beforo us we can distinctly perceive numerous transverse lines crossing the course of the bristles at right angles. If these transverse lines indicate a periodical check to the growth of the baleen, then the age of the B. maximus would be 800 to 900 years old, that being the number of transverse lines on the longest plate of baleen. (Knox, Cat. Prep. Whale,' 9.) "The whalebone of the smooth-bodied whales without any back fins (Balcena) is elongate, much longer than broad at the base, and gradually attenuated, and edged with a fringe of equal lengthened fine soft bristles. The baleen is internally formed of a thin layer of fibres, covered on each side with a thick coat of enamel ;' when dry and out of the mouth the blades are fiat "The whalebone of the plaited-bellied whale with a bunch (Mesa ptera) or a dorsal fin (Balcenoptera) is short, broad, triangular, not much longer than broad at the base, and rapidly attenuated ; and is edged with a series (sometimes rather crowded) of elongate rigid unequal bristle-like fibres, which become much thicker and more rigid near and at the tip. The baleen is internally formed of a more or less thick layer of thick fibres, covered on each side with a thin layer of enamel, and when dry and out of the palate they are curled up and somewhat spirally twisted.