204. 



NATURE 



\_Dcc. 30, 1880 



allied than our primordial hippoids are with their de- 

 scendants. Yet, according to existing arrangements, the 

 ancestors would have to be placed in one order of the 

 class of mammalia and their descendants in another. It 

 may be suggested that it might be as well to wait until the 

 primordial hippoid is discovered before discussing the 

 difficulties which will be created by its appearance. But 

 the truth is that that problem is already pressing in an- 

 other shape. Numerous "lemurs," with marked ungulate 

 characters, are being discovered in the older Tertiaries of 

 the United States and elsewhere ; and no one can study 

 the more ancient mammals with which we are already 

 acquainted without being constantly struck with the in- 

 sectivorous characters which they present. In fact, there 

 is nothing in the definition of cither Primates, Carnivores, 

 or Ungulates, which affords any means of deciding whether 

 a given fossil skeleton, with skull, teeth, .ind limbs almost 

 complete, ought to be ranged with the Lemurs, the Insec- 

 tivores, the Carnivores, or the Ungulates. 



In whatever order of mammals a sufficiently long series 

 of forms has come to light, they illustrate the three-fold law 

 of evolution as clearly, though perhaps not so strikingly, 

 as the equine series does. Carnivores, Artiodactyles, and 

 Persso-sodactyles all tend, as we trace them back through 

 the Tertiary epoch, towards less modified forms which will 

 fit into none of the recognised orders, but come closer to 

 the Insectivora than to any other. It would, however, be 

 most inconvenient and misleading to term these primor- 

 dial forms Insectivora, the mammals so-called being 

 themselves more or less specialised modifications of the 

 same common type, and only, in a partial and limited 

 sense, representatives of that type. The root of the 

 matter appears to me to be that the palxontological facts 

 which have come to light in the course of the last ten or 

 fifteen years have completely broken down existing taxo- 

 nomical conceptions, and that the attempts to construct 

 fresh classifications upon the old model are necesssarily 

 futile. The Cuvieran method, which all modern classifiers 

 have followed, has been of immense value in leading 

 to the close investigation and the clear statement of the 

 anatomical characters of animals. But its principle, the 

 association into sharp logical categories defined by such 

 characters, was sapped when Von Baer showed that, in 

 estimating the likenesses and unlikenesses of animals, 

 development must be fully taken into account ; and if the 

 importance of individual development is admitted, that of 

 ancestral development necessarily follows. If the end of 

 all zoological classification is a clear and concise expres- 

 sion of the morphological resemblances and difterences 

 of animals, then all such resemblances must have a taxo- 

 nomic value. But they fall under three heads : (i) those 

 of adult individuals ; (2) those of successive stages of 

 embryological development or individual evolution ; (3) 

 those of successive stages of the evolution of the species, 

 or ancestral evolution. An arrangement is " natural," 

 that is, logically justifiable, exactly in so far as it ex- 

 presses the relations of likenesses and unlikenesses enu- 

 merated under these heads. Hence, in attempting to 

 classify the Mammalia, we must take into account not 

 only their adult and cmbryogenetic characters, but their 

 morphological relations, in so far as the several forms 

 represent difterent stages of evolution. And thus, just 

 as the persistent antagonism of Cuvier and his school to 

 the essence of Lamark's teachings (imperfect and objec- 

 tionable as these often were in their accidents) turns 

 out to have been a reactionary mistake, so Cuvier's 

 no less definite repudiation of the principle of Bonnet's 

 "c'chclk dcs cti'fs" was no less unfortunate. The 

 existence of a " scala animantium," is a necessary 

 consequence of the fdoctrine of evolution, and its 

 establishment constitutes, I believe, the foundation 

 of scientific taxonomy. Many years ago, in my lec- 

 tures at the Royal College of Surgeons, I particularly 

 insisted on the central position of the Insectivora among 



the higher Mammalia; and further study of this order 

 and of the Rodentia has only strengthened my conviction 

 that any one who is acquainted with the range of variation 

 of structure in these groups possesses the key to every 

 peculiarity which is met with in the Primates, the Carni- 

 vora, and the Ungulata. Given the common plan of the 

 Insectivora and of the Rodentia, and granting that the 

 modifications of the structure of the limbs, of the brain, 

 and of the alimentary and reproductive viscera which 

 occur among them may exist and accumulate elsewhere, 

 and the derivation of all Eutheria from animals which, 

 e.xcept for their diffuse placentation, would be Insectivores, 

 is a simple deduction from the law of evolution. I venture 

 to express a confident expectation that investigation into 

 the mammalian fauna of the Mesozoic epoch will, sooner 

 or later, fill up the blanks which at present exist in the 

 " scala mammalium." Prof Huxley proceeded to give 

 details on which his conclusions were based, and dwelt 

 on the fact that much further careful work is needed 

 to clear up problems before us. 



NOTES 



We are enabled through the courtesy of the Council of the 

 Royal Society of Edinburgh to present our readers with an 

 abstract of a remarkable paper by Mr. John Aitken, on 

 Dust, Fog and Mist. The paper opens up new lines 

 of. inquiry, and indeed a new future, to what has hitherto 

 been one of the most jdifficult branches of meteorology, viz. 

 the investigation of the vapour of the atmosphere, which we 

 may safely predict meteorologists will not be slow in following 

 up. Mr. Aitken continues the prosecution of the inquiry, and 

 we learn that last week he has experimented with tempera- 

 tures as low as 14° 'O F. with the result that equally as at 

 higher temperatures, there is no cloudy conden.^ation when there 

 is no dust ; but, when there is dust, cloudy condensation takes 

 place on the dust nuclei, the amount of cloudiness being of 

 course relatively small at such low temperatures on account of 

 the small amount of vapour present. Taken along with Prof. 

 Lister's experiments, in which it was shown that a single 

 drop of rain developed organisms in sensitive solutions which' 

 would otherwise have remained for months unaltered, it shows 

 that germ-producing matter, or germs themselves, form at 

 least a part of the cloud- and fog-producing dust. Hence a 

 cotton-wooI respirator may prove a protection against disease. 

 We have said enough tojshow that the paper is one of interest, 

 not only to the physicist and the meteorologist, but also (and 

 perhaps even specially) to the physiologist and the sanitarian. 



We are pleased to learn that Dr. W. De La Rue, F.R.S., 

 has been chosen a Corresponding Member of the Paris Academy 

 of Sciences in the Section of Astronomy. 



Baron de Chaudoir, Mr. McLachlan, and Baron C. R. 

 Osten-Sacken have been elected honorary members of the Ento- 

 mological Society of Belgium, fiUing the vacancies in the list 

 caused by the deaths of Dr. Boisduval, M. Mulsant, and Dr. 

 Snellen van Vollenhoven. 



It is proposed to hold a meeting of the Association for the 

 Improvement of Geometrical Teaching on 'Friday, January 7, 

 in the Botanical Theatre of University College, Gower Street, 

 at II a.m. The .sub-committees appointed January 11, 1878, 

 have prepared, and circulated amongst the members, draft 

 syllabuses of solid geometry, higher plane geometry, and geo- 

 metrical conies, and will present their Reports at the meeting. 

 All persons interested in the elementary teaching of geometry 

 are invited to attend. 



According to a resolution of the St. Petersburg Society of 

 Naturalists, the work of Prof. Wagner on " Medusa: and 



