6o6 



SCIENTIFIC NEWS. 



[Dec. 14, iJ 



ol these coveted trophies, that it might be dedicated to 

 some idol deity, or take first place among the treasures 

 of the regal dwelling. 



In the black whales, two or three species of which 

 are recognised, the teeth are also very large and strong, 

 averaging some nine inches in total length, of which as 

 nearly as possible two-thirds are buried in the gum and 

 the jaw-bone. The base of each tooth is hollowed to a 

 distance of several inches, but its substance is, neverthe- 

 less, so dense and heavy that even a dried tooth will 

 often weigh from sixteen to eighteen ounces. 



A most remarkable modification of the dental arma- 

 ture we find in the narwhal, whose lower teeth are 

 absolutely wanting, while those of the upper jaw are 

 represented by two only. In the female animal even 

 these two are not, as a rule, developed ; without teeth she 

 is born, and without teeth she lives and dies. But in the 

 male, one at least, which probably represents the left 

 upper canine, is invariably developed in a most astonish- 

 ing degree, and assumes the form of a itapering, spiral 

 rod of ivory some eight or nine feet in length ; and not 

 very uncommonly the other is developed with it. A 

 very fine example of a two-tusked, narwhal, for instance, 

 may be seen in the museum at Hull. 



But, as a general rule, one tusk only is present, the 

 corresponding tooth remaining throughout life in a 

 rudimentary condition. And what the function or 

 functions of this tusk may be is still a matter of conjec- 

 ture. Many theories, however, have been put forward 

 upon the subject, most of them based upon the fact that 

 the tip of the tusk is always smooth and polished, as 

 though by incessant use, while the remainder is more or 

 less encrusted, and is evidently not subjected to regular 

 friction. Thus it has been urged that the animal employs 

 its weapon for spearing fish, driving at them very much 

 as a mediaeval knight, his lance in rest, rode at a 

 mounted foe. But this theory will not bear examina- 

 tion, and is open to two fatal objections. How, in the 

 first place, supposing that the narwhal does so transfix 

 its victims, is it to remove them from its spear and 

 transfer them to its mouth ? For it has no limbs 

 available for such a purpose. Is it to be incessantly 

 tantalised b} r the sight of food in close proximity to its 

 jaw, which no efforts of its own will enable it to devour? 

 And, moreover, if such be the duty of the tusk, why is 

 it wanting in the female ? For only in exceptional cases 

 does she possess it. 



Another theory, adopted by Fabricius, is to the effect 

 that the tusk is employed in opening ice-holes in the 

 huge floes which in winter cover the northern seas. But 

 again, if this be so, why has Nature omitted to supply 

 the organ in question to the female narwhal, whose need 

 of air is as great as that of her mate ? And how is the 

 animal, supposing it to be capable of maintaining a per- 

 pendicular position in the water, to revolve while the 

 boring operation is in progress ? Such a feat, from its 

 very structure, is absolutely impossible. 



A third theorist suggests that the animal, when in want 

 of food, descends to the depths of ocean, and stirs up 

 the mud with its tusk in order to disturb any flat fish 

 which may be lying upon it, recognising the fact that 

 while at rest they assimilate so exactly to their surround- 

 ings that the keenest eye cannot detect them. But this 

 theory, a somewhat fanciful one at best, is again nega- 

 tived by the sexual difference already referred to. 



Seeing that the tusk, broadly speaking, is a masculine 

 appendage only, the probability is that it is employed as 



a weapon, not in the capture of prey, but in those combats 

 which are frequent among male animals, more especially 

 during the earlier part of the breeding season. We know 

 that the male seals and walruses fight with great ferocity 

 at that period, just as do many of the terrestrial mammals ; 

 and seals and walruses are at any rate allied to the 

 cetaceans. And we have it, moreover, upon no less 

 authority than that of Scoresby, the celebrated traveller 

 and explorer, that quite large companies of male narwhals 

 are sometimes to be seen gambolling together, crossing 

 their long tusks, and fencing like experienced swordsmen. 

 And it is more than likely that during the season of pair- 

 ing such mimic warfare gives place to battle in grim 

 earnest. Even if such be the case, however, it is still 

 hard to account for the highly polished condition of the 

 last few inches of the tusk, which part alone seems to be 

 in constant use, and to be subjected to friction. Thus it 

 may well be that the weapon in question has its supple- 

 mentary uses, although we have as yet failed to discover 

 them. 



Although the female narwhal is not, as a rule, armed 

 after the manner of her formidable mate, specimens ot 

 the gentler sex are occasionally taken in which the tusk 

 is present ; and at least two cases have been recorded in 

 which both canines, in the female animal, were similarly 

 developed. In one of these cases the one tusk was 

 seven feet and five inches long, and the other seven feet. 

 Most probably females so armed are barren, their repro- 

 ductive energies being diverted into other channels, and 

 bringing about the assumption of characters ordinarily 

 denied to them. And we have an analogous case in the 

 crowing and spur-bearing hens which are occasionally 

 met with, and from which eggs may be expected in 

 vain. 



Very few of the toothed cetaceans at all resemble one 

 another in their dentition, and the number of the teeth is 

 especially variable. Thus, in the narwhal, as we have 

 seen, only one is usually developed. In the Mcsoplodons, of 

 which Sowerby's whale may be taken as a type, and 

 also in the Ziphii, two rather large teeth are present, one 

 upon either side of the lower jaw. In the pilot whale, 

 however, there are ninety-six, evenly divided upon either 

 side of the mouth. The porpoise possesses from eighty 

 to one hundred and four, the dolphin irom one hundred 

 and sixty to two hundred, while the pontoporia, an 

 inmate of certain South American rivers, bears off the 

 palm with from two hundred and twelve to two hundred 

 and twenty-two. In these last the teeth are sometimes 

 very irregularly distributed. Thus, in the jaw of a 

 Gangetic dolphin were found the singular number of one 

 hundred and seventeen teeth, fifty-seven being situated 

 upon one side of the mouth, and sixty upon the other. 

 In apportioning teeth to the cetaceans, in fact, Nature 

 almost seems to have laid rules aside altogether, and to 

 have left both number and position of those organs pretty 

 well to mere chance, alike in the species and in the in- 

 dividual. 



«-3*JHffe-. ■ 



T hcoretical Mechanics. By J. Edward Taylor, M.A., 

 London. London : Longmans, Green, and Co. 



One of the few tangible advantages ot the present 

 system of examination is, that they create a demand 

 for manuals of elementary science. It is, however, 

 characteristic of such text-books to find that, as in the 



