652 



NA TURE 



[October 31, 1901 



the mean position of the centre as g7°"i + i5"2 from 

 thirteen observations by various observers. In the 

 " General Catalogue of Radiant Points " {Memoirs R.A.S., 

 vol. liii.) this shower forms No. Ixxix. and the radiant is 

 given at 96'-6 + i6''-5, based on nineteen observations. 

 But there is now reason to believe that these positions 

 are two or three degrees north of the correct place and 

 that instead of corresponding with the star y Geminorum 

 it really agrees with ^ Geminorum. Certainly in 1900 

 and 1901 the most conspicuous shower of rapid streak- 

 leaving meteors was directed from 100' + 13', the posi- 

 tion of the star ^ Geminorum for January 1901 being 

 a = 6h. 39m. 44'os., 8 = 13" o' 9 "'I +. 



It will be interesting to watch future returns of the 

 October meteors in order to ascertain whether the formerly 

 strong shower at v Orionis has only been temporarily 

 weak during the few past years or whether it has finally 

 withdrawn in favour of its easterly companion radiant at 

 f Geminorum. Possibly the swarm of Orionids has been 

 recently disturbed by planetary attraction and the node 

 displaced sufficiently to bring about a change of 9" in 

 the radiant. If so, the principal meteoric display of 

 October must henceforth be known as Geminids instead 

 of Orionids. ISut the more probable supposition appears 

 to be that the Orionids have been very scantily dis- 

 tributed along those parts of their orbit traversed by the 

 earth in late years, whereas the neighbouring shower in 

 Gemini has been so much stronger than usual as to form 

 the principal display of the epoch. The Orionid system 

 used to present itself with considerable regularity like 

 the August Perseids, though it exhibited variations of 

 strength in part no doubt attributable to the different 

 atmospheric conditions prevailing, to the position and 

 age of the moon and to other circumstances capable of 

 affecting the visible aspect of the stream. 



W. F. Denning. 



ARMOUR-CLAD WHALES. 



A MONG the many wonderful palasontological dis- 

 -'^ coveries that have startled the scientific world 

 during the last few years, none, perhaps, is more un- 

 e.xpected than the revelation that the ancestral whales 

 were protected from attack by a bony armour analogous 

 to that with vv-hich the armadillos of South America are 

 covered. Scarcely less marvellous is the fact that 

 vestiges of this ancient coat of mail are still borne by 

 such familiar cetaceans as the porpoise and its near 

 relative the Japanese porpoise {Neophocaena phocae- 

 noidc's), the latter species being distinguished by the 

 absence of a back-fin. That creatures like the modern 

 pelagic whales and porpoises, or even the river dolphins, 

 could ever have been invested with a complete bony 

 armour is, of course, an absolute impossibility. The 

 rigidity of such a panoply would have interfered far too 

 much with the mobility of their supple bodies, while its 

 weight would have impaired their buoyancy. Con- 

 sequently it is necessary to assume that in even the 

 earlier representatives of these types the armour must 

 have been in a condition of degradation and elimination, 

 so that we must go back to still earlier forms to find it in 

 its full development. As every one knows nowadays, 

 whales and dolphins trace their ancestry to land animals, 

 and it appears highly likely that when such ancestral 

 creatures began to take to an amphibious life on the 

 sea-shore, or at the mouth of a large river, they may 

 have developed a dermal armour which would serve to 

 protect them alike from the breakers and from the attacks 

 of sharks and other marine monsters. For the idea that 

 the terrestrial ancestors of the cetaceans were clad in 

 armour cannot for a moment be entertained, since the 

 primitive mammals were not so protected and the 



NO. 1670, VOL. 64] 



American armadillos afford an instance of the develop- 

 ment de Hoz'o of such a bony panoply at a comparatively 

 recent epoch. 



Years ago the late Dr. H. Burmeister described a 

 porpoise from Argentina as Phocaena spinipinnis, on 

 account of its possessing a number of spiny tubercles 

 embedded in the skin in the neighbourhood of the back- 

 fin as well as on the fin itself. " Some small spines," he 

 writes, "begin in the middle of the back, at the distance 

 of 25 centimetres in front of the fin, as a single line of 

 moderate spines ; but soon another line begins on each 

 side, so that in the beginning of the fin there are already 

 three lines of spines. These three lines are continued 

 over the whole rounded anterior margin of the fin and 

 are augmented on both sides by other small spines 

 irregularly scattered, so that the whole number of lines 

 of spines in the middle of the fin is five." In a section 

 of the skin of the back-fin the tubercles are distinctly 

 seen, many of them being double. 



Similar tubercles were described on the back-fin of a 

 porpoise taken in the Thames in 1865 ; and quite re- 

 cently a row of no less than twenty-five well-developed 

 tubercles has been detected on the front edge of the 

 back-fin of a fcetal porpoise, these tubercles being nearly 

 white and thus showing up in marked contrast to the 

 dark-coloured skin. Even more distinct are the tubercles 

 in the skin of the finless back of the Japanese porpoise, 

 where they form several rows of polygonal plates. 



In a fossil porpoise {Dclphinopsis frcyeri) from the 

 middle Tertiary deposits of Radoboj in Croatia, the 

 tubercles were still more strongly developed, and formed 

 a series of regularly arranged and parallel rows in the 

 neighbourhood of the back-fin. They clearly indicate 

 one step from the modern porpoises in the direction of a 

 species provided with a functional bony armour in this 

 region of the body. Between the extinct Croatian por- 

 poise and the much more ancient whale known as 

 Zcuglodon, some part of whose body was protected by a 

 bony armour as solid as that of the giant extinct relatives 

 of the modern armadillos, the intermediate links are at 

 present unknown, although they may turn up any day. 

 Zeiiglodon was first discovered in the early Tertiary 

 strata of the United States, but its remains have subse- 

 quently been obtained from the equivalent deposits of 

 Egypt and elsewhere, and in early times it was probably 

 the dominant cetacean of the world. Years ago there 

 were discovered with the bones of the internal skeleton of 

 this whale a number of bony plates which originally 

 formed a dermal armour ; although they were regarded 

 as belonging to a species of leathery turtle and as having 

 nothing to do with the whale. 



But in microscopic structure, as well as in their ar- 

 rangement, these polygonal bony plates differ altogether 

 from the armour of the leathery turtle ; while their struc- 

 ture is generally similar to the undoubted bones ot 

 Zeiiglodon with which they are found in association. 

 Moreover, a fragment covered on one side with armour ot 

 this type has been discovered which cannot, apparently, 

 be any part of the shell of a turtle, but which may well be 

 the back-fin of Zeiiglodon. And as the aforesaid bony 

 tubercles of the porpoises are always found on or near 

 the back-fin, it is a safe assumption that in Zeiiglodon 

 the entire dorsal fin, as well as some portion of the 

 back, was covered with a complete tessellated armour of 

 bony plates. 



The majority of the living toothed whales (inclusive of 

 porpoises and dolphins) are furnished with a dorsal fin, . 

 and it is therefore reasonable to suppose (apart from the 

 evidence of the specimen just referred to) that Zcin^lodoii 

 was similarly provided ; and if this be so, that cetacean 

 was evidently a pelagic creature. For the function of a 

 dorsal fin is to act as a kind of keel in maintaining the 

 balance of the body, this appendage being most 



