July 5, 1883] 



NA TURE 



'.2J 



sufficient have been supplied by gradual changes taking 

 place, some of the stages of which are seen in the inter- 

 mediate conditions still exnibited in the Megaptera, and 

 the Atlantic and Southern Right Whales. Befo-e de- 

 scribing the extreme modifications in the direction of com- 

 plexity, I may mention, to show the range at present 

 presented in the development of baleen, that there has 

 lately been discovered in the North Pacific a species 

 called by the whalers the Californian Gray Whale {Rackia- 

 nectes glaucus), which shows the opposite extreme of 

 simplicity. The animal is from 30 to 40 feet in length ; 

 the baleen blades are only 182 on each side (according to 

 Scaminon) and far apart, very short (the longest being from 

 14 to 16 inches in length), light brown or nearly white in 

 colour, and still more coarse in grain and inelastic than 

 that of the Rorquals. The food of these whales is not 

 yet known with certainty. They have been seen appa- 

 rently seeking for it along soft bottoms of the sea, and 

 fuci and mussels have been foun 1 in their stomachs. 



In the Greenland Right Whale of the circumpolar seas, 

 the Bow-head of the American whalers {Balccna mysli- 

 cetus), all the peculiarities which distinguish the head and 

 mouth of the whales from other mammals have attained 

 their greatest development. The he id is of enormous 

 size, exceeding one-third of the whole length of the crea- 

 ture. The cavity of the mouth is actually larger than 

 that of the body, thorax and ablomen together. The 

 upper jaw is very narrow, but greatly arched from before 

 backwards, to increase the height of the cavity and allow 

 for the great length of the baleen, the enormous rami of 

 the mandibles are widely separated posteriorly, and have 

 a still further outward sweep before they meet at the 

 symphysis in front, giving the floor of the mouth the 

 shape of an immense spoon. The baleen blades attain 

 the number of 350 or more on each side, and those in the 

 middle of the series have a length of ten or even twelve 

 feet. They are b! ick in colour, fine and highly elastic in 

 texture, and fray out at the inner edge and ends into long 

 delicate, soft, almost silky, but very tough hairs. 



How these immensely long blades depending vertically 

 from the palate were packed into a mouth the height of 

 which was scarcely more than half their length, was a 

 mystery not solved until a few years ago. Capt. David 

 Gray of Peterhead, at my request, first gave us a clear 

 idea of the arrangement of the baleen in the Greenland 

 whale, and showed that the purpose of its wonderful 

 elasticity was not primarily at least the benefit of the 

 corset and umbrella makers, but that it was essential for 

 the correct performance of its functions. It may here 

 be mentioned that the mo lification of the mouth struc- 

 ture of the Right Whale is entirely in relation to its food. 

 It is by this apparatus that it is enabled to avail itself of 

 the minute but highly nutritious crustaceans and ptero- 

 pods which swarm in im nense shoals in the seas it fre- 

 quents. The large mouth enables it to take in at one 

 time a sufficient quantity of water filled with these small 

 organisms, and the length and delicate structure of 

 the baleen provides an efficient strainer or hair sieve 

 by which the water can be drained off. If the baleen 

 were, as in the Rorquals, short and rigid, and only 

 of the length of the aperture between the upper and 

 lower jaws when the mouth was shut, when the jaws 

 were separated a sp ice would be left beneath it through 

 which the water and the minute particles of food 

 would escape together. But instead of this, the long, 

 slender, brush-like ends of the whalebone blades, when 

 the mouth is closed, fold back, the front ones pass- 

 ing below the hinder ones in a channel lying between 

 the tongue and the bone of the lower jaw. When the 

 mouth is opened their elasticity causes them to straighten 

 out like a bow that is unbent, so that at whatever 

 distance the jaws are separated, the strainer remains iu 

 perfect action, filling the whole of the interval. The mecha- 

 nical perfection of the arrangement is completed by the 



great development of the lower lip, which rises stiffly 

 above the jaw-bone, and prevents the long, slender, 

 flexible ends of the baleen being carried outwards by the 

 rush of water from the mouth, when its cavity is being 

 diminished by the closure of the jaws and raising of the 

 tongue. The interest and admiration excited by the 

 contemplation of such a beautifully adjusted piece of 

 mechanism is certainly heightened by the knowledge 

 that it has been brought about by the gradual adapta- 

 tion and perfection of structures common to the whole 

 class of animals to which the whale belongs. 



Few points of the structure of whales offer so great a 

 departure from the ordinary mammali in type as the 

 limbs. The fore limbs are reduced to the condition of 

 simple paddles or oars, variously shaped, but always 

 flattened and more or less oval in outline. They are 

 freely movable at the shoulder joint, where the humerus 

 or upper-arm bone articulates with the shoulder-blade 

 in the usual manner, but beyond this point, except 

 a slight flexibility and elasticity, there is no motion 

 between the different segments. The bones are all 

 there, corresponding in number and general relations 

 with those of the human or any other mammalian 

 arm, but they are flattened out, and their contiguous 

 ends, instead of presenting hinge-like joints, come 

 in contact by flat surfa:es, united together by strong 

 ligamentous bands, and all wrapped up in an un- 

 divided covering of skin, which allows externally of no 

 sign of the separate and many-jointed fingers seen in the 

 skeleton. 



Up to the year 1865 it was generally thought that there 

 was nothing to be found between this bony framework and 

 the covering skin, with its inner layer of blubber, except 

 dense fibrous tissue, with blool-vessels and nerves suffi- 

 cient to maintain its vitality. Dissecting a large Rorqual, 

 67 feet in length, upon the beach of Pevensey Bay in that 

 year, I was surprised to find lying upon the bones of the 

 fore-arm well-developed muscles, the red fibres of which 

 reached nearly to the lower end of these bones, ending 

 in strong tendons, passing to, and radiating out on, the 

 palmar surface of the hand. Circumstances then pre- 

 vented me following out the details of their arrangement 

 and distribution, but not long afterwards Prof. Struthers 

 of Aberdeen had an opportunity of carefully dissecting 

 the fore-limb of another whale of the same species, and 

 he has- recorded and figured his observations in the 

 Journal of Anatomy for November, 1871. He found on 

 the internal or palmar aspect of the limb three distinct 

 muscles corresponding in attachments to the flexor carpi 

 ulnaris, the flexor profundus d gitorum, and the flexor 

 longus pollicis of man, and on the opposite side but one, 

 the extensor communis digitorum. ' Large as the-^e muscles 

 actually are, yet, compared with the size of the animal, 

 they cannot but be regarded as rudimentary and being at- 

 tached to bones without regular joints and firmly held to- 

 gether byunyielding tissues, theirfunctions must be reduced 

 almost to nothing. But rudimentary as the muscles of 

 the Fin-whales are, lower stages of degradation of the 

 same structures are found in other members of the group. 

 In some they are indeed present in form, but their 

 muscular structure is gone and they are reduced in most 

 of the toothed whales to mere fibrous bands, scarcely 

 distinguishable from the surrounding tissue which con- 

 nects the inner surface of the skin with the bone. It is 

 impossible to contemplate these structures without having 

 the conviction forced home that here are the remains of 

 parts once of use to their possessor, now, owing to the 

 complete change of purpose and mode of action of the 

 limb, reduced to a condition of atrophy verging on com- 

 plete disappearance. 



The changes that have taken place in the hind-limbs 

 are even more remarkable. In all known Cetacea (unless 



1 The muscles of the forearm of an allied species, Bafanoptera rostraia, 

 were described by Macalister in 1868, and Perrin in 1870. 



