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NATURE 



{June 28, 1883 



The important and interesting problem of the origin of 

 .he Cetacea and their relations to other forms of life is at 

 present involved in the greatest obscurity. They present 

 no more signs of affinity with any of the lower classes of 

 vertebrated animals than do many of the members of 

 their own class. Indeed in all that essentially distin- 

 guishes a mammal from one of the oviparous vertebrates, 

 whether in the osseous, nervous, vascular, or reproductive 

 systems, they are as truly mammalian as any, even the 

 highest, members of the class. Any supposed signs of 

 inferiority are, as we shall see, simply modifications in 

 adaptation to their peculiar mode of life. Similar modi- 

 fications are met with in another quite distinct group of 

 mammalia, the Sirenia, and also, though in a less complete 

 degree, in the aquatic Carnivora or seals. But these do not 

 indicate any community of origin between these groups 

 and the Cetacea. In fact, in the present state of our 

 knowledge, the Cetacea are absolutely isolated, and little 

 satisfactory reason has ever been given for deriving them 

 from any one of the existing divisions of the class more than 

 from any other. The question has indeed often been 

 mooted whether they have been derived from land 

 mammals at all, or whether they may not be the survivors 

 of a primitive aquatic form which was the ancestor not 

 nnly of the whales, but of all the other members of the 

 class. The materials for — I will not say solving — but for 

 throwing some light upon this problem, must be sought 

 for in two regions — in the structure of the existing 

 members of the order, and in its past history, as revealed 

 by the discovery of fossil remains In the present state 

 of science it is chiefly on the former that we have to rely, 

 and this therefore will first occupy our attention. 



One of the most obvious external characteristics by 

 which the mammalia are distinguished from other classes 

 nf vertebrates is the more or less complete clothing of 

 the surface by the peculiar modification of epidermic 

 tissue called hair. The Cetacea alone appear to be ex- 

 ceptions to this generalisation. Their smooth, glistening 

 exterior is, in the greater number of species, at all events 

 in adult life, absolutely bare, though the want of a hairy 

 covering is compensated for functionally by peculiar 

 modifications of the structure of the skin itself, the epi- 

 dermis being greatly thickened, and a remarkable layer 

 of dense fat closely incorporated with the tissue of the 

 derm or true skin ; modifications admirably adapted for 

 retaining the warmth of the body, without any roughness 

 of surface which might occasion friction and so interfere 

 with perfect facility of gliding through the water. Close 

 examination, however, shows that the mammalian charac- 

 ter of hairiness is not entirely wanting in the Cetacea, 

 although it is reduced to a most rudimentary and appar- 

 ently functionless condition. Scattered, small, and gene- 

 rally delicate hairs have been detected in many species, 

 both of the toothed and of the whalebone whales, 

 but never in any situation but on the face, either 

 in a row along the upper lip, around the blowholes or 

 on the chin, apparently representing the large, stiff 

 " vibrissas '' or " whis ;ers " found in corresponding situ- 

 ations in many land mammals. In some cases these 

 seem to persist throughout the life of the animal; more 

 often they are only found in the young or even the fcetal 

 stite. In some species they have not been detected at 

 any age. 



Eschricht and Reinharjt counted in a new born Green- 

 land Right Whale (Balana mysticetus) sixty-six hairs near 

 the extremity of the upper jaw, and about fifty on each side 

 of the lower lip,as well as a few around the blowholes, where 

 they have also been seen in Mcgaplcra longimana and 

 Balcenoptcra rostrata. In a large Rorqual [Balmnoptera 

 musculus), quite adult and sixty-seven feet in length, 

 stranded in Pevensey Bay in 1865, there were twenty-five 

 white, straight, stiff hairs about half an inch in length, 

 scattered somewhat irregularly on each side of the verti- 

 cal ridge in which the chin terminated, extending over a 



space of nine inches in height and two and a half inches 

 in breadth. The existence of' these rudimentary hairs 

 must have some significance beyond any possible utility 

 they may be to the anim il Perhaps some better ex- 

 planation may ultimately be found for them, but it must 

 be admitted that they are extremely suggestive that we 

 have here a case of heredity or conformation to a type of 

 ancestor with a full hairy clothing, just on the point of 

 yielding to complete adaptation to the conditions in which 

 whales now dwell. 



In the organs of the senses the Cetacea exhibit some 

 remarkable adaptive modifications of structures essen- 

 tially formed on the Mammalian type, and not on that 

 characteristic of the truly aquatic Vertebrates, the fishes, 

 which, if function were the only factor in the production 

 of structure, they might be supposed to resemble. 



The modifications of the organs of sight do not so 

 mu;h affect the eyeball as the accessory apparatus. To 

 an animal whose surface is always bathed with fluid, the 

 complex arrangement which mammals generally possess 

 for keeping the surface of the transparent cornea moist 

 and protected, the movable lids, the nictitating mem- 

 brane, the lacrymal gland, and the arrangements for 

 collecting and removing the superfluous tears when they 

 have served their function cannot be needed, and hence 

 we find these parts in a most rudimentary condition or 

 altogether absent. In the same way the organ of hearing 

 in its essential structure is entirely mammalian, having 

 not only the sacculi and semicircular canals common to 

 all but the lowest vertebrates, but the cochlea, and tym- 

 panic cavity with its ossicles and membrane, all, however, 

 buried deep in the solid substance of the head ; while the 

 parts specially belonging to terrestrial mammals, those 

 which collect the vibrations of the sound travelling 

 through air, the pinna and the tube which conveys it to 

 the sentient structures within are entirely or practically 

 wanting. Of the pinna or external ear there is no trace. 

 The meatus auditorius is certainly there, reduced to a 

 minute aperture in the skin like a hole made by the prick 

 of a pin, and leading to a tube so fine and long that it 

 cannot be a passage for either air or water, and therefore 

 can have no appreciable function in connection with the 

 organ of hearing, and must be classed with the other 

 numerous rudimentary structures that whales exhibit. 



The organ of smell, when it exists, offers still more re- 

 markable evidence of the origin of the Cetacea. In fishes 

 this organ is specially adapted for the perception of 

 odorous substances permeating the water ; the termina- 

 tions of the olfactory nerves are spread over a cavity 

 near the front part of the nose, to which the fluid in which 

 the animals swim has free access, although it is quite un- 

 connected with the respiratory passages. Mammals, on 

 the other hand, smell substances with which the atmo- 

 sphere they breathe is impregnated ; their olfactory nerve 

 is distributed over the more or less complex foldings of 

 the lining of a cavity placed in the head, in immediate 

 relation to the passages through which air is continually 

 driven to and fro on its way to the lungs in respiration, 

 and therefore in a most favourable position for receiving 

 impressions from substances floating in that air. The 

 whalebone whales have an organ of smell exactly on the 

 mammalian type, but in a rudimentray condition. The 

 perception of odorous substances diffused in the air, upon 

 which many land mammals depend so much for obtaining 

 their food, or for protection from danger, can be of little 

 importance to them. In the more completely modified 

 Odontocetes the olfactory apparatus, as well as that part 

 of the brain specially related to the function of smell is 

 entirely wanting, but in both groups there is not the 

 slightest trace of the specially aquatic olfactory organ of 

 fishes. Its complete absence and the vestiges of the 

 aerial organ of land mammals found in the Mystacocetes 

 are the clearest possible indications of the origin of the 

 Cetacea from air-breathing and air-smelling terrestrial 



