Sept. 8, 1 88 1 J 



NA TURE 



453 



professor of anatomy in Florence, though a Dane by birth. 

 Collectors of fossils at that day -ivere familiar with certain bodies 

 termed "glossopetrse," and speculation was rife as to their 

 nature. In the first half of the seventeenth century, F.abio 

 Colonna had tried to convince his colleagues of the famous 

 Accademia dei Lincei that the glossopetrx- were merely fo=sil 

 sharks' teeth, but his arguments made no impression. Fifty 

 years later Steno re-opened the question, and, by dissecting the 

 head of a shark and pointing out the very exact correspondence 

 of its teeth with the glossopetra;, left no rational doubt as to the 

 origin of the latter. Thus far, the work of Steno went little 

 further than that of Colorma, but it fortunately occurred to him 

 to think out the whole subject of the interpretation of fossils, and 

 the results of his meditations was the publication, in 1669, of a 

 little treatise with the very quaint title of "De Solido intra Solidum 

 naturaliter contento." The general course of Steno's ai'gument 

 may be stated in a few words. Fossils are solid bodies which by 

 some natural process have come to be contained within other 

 solid bodies — namely, the rocks in which they arc imbedded ; 

 and the fundamental problem of palaeontology, stated generally, 

 is tills — "Given a body endowed with a certain shape and 

 produced in accordance with natural laws, to find in that body 

 itself the evidence of the place and manner of its production.'' 

 The only way of solving this problem is by the application of 

 the axiom that " like effects imply like causes," or as Steno puts 

 it, in reference to this particular case, that "bodies which are 

 altogether similar have been produced in the same way."- 

 Hence, since the glossopetra; are altogether similar to sharks' 

 teeth, they must have been produced by shark-like fishes ; and 

 since many fossil shells correspond, down to the minutest details 

 of structure, with the shells of existing marine or freshwater 

 animals, they must have been produced by similar animals ; 

 and the like reasoning is applied by Steno to the fossil 

 bones of vertebrated animals, whether aquatic or terrestrial. To 

 the obvious objection that many fossils are not altogether 

 similar to their living analogues, differing in substance while 

 agreeing in form, or being mere hollows or impressions, the 

 surfaces of which are figured in the same way as those of animal 

 or vegetable organisms, Steno replies by pointing out the changes 

 which take place in organic remains imbedded in the earth, and 

 how their solid substance may be dissolved away entirely, 

 or replaced by mineral matter, until nothing is left of the 

 original but a cast, an impression, or a mere trace of its contours. 

 The principles of investigation thus excellently stated and 

 illustrated by Steno in 1669, are those which have, consciously, 

 or unconsciously, guided the researches of pala:ontologists ever 

 since. Even that feat of palaeontology which has so powerfully 

 impressed the popular imagination, the reconstruction of an 

 extinct animal from a tooth or a bone, is based upon the simplest 

 imaginable application of the logic of Steno. A moment's 

 consideration will show, in fact, that Steno's conclusion that the 

 glossopetr;e are sharks' teeth implies the reconstruction of an 

 animal from its tooth. It is equivalent to the assertion that the 

 animal of which the glossopetra; are relics had the form and 

 organisation of a shark ; that it had a skull, a vertebral column, 

 and limbs similar to tho^e which are characteristic of this group 

 of fishes ; that its heart, gills, and intestines presented the 

 peculiarities which those of all sharks exhibit ; nay, even that any 

 hard parts which its integument contained were of a totally 

 different character from the scales of ordinary fishes. These 

 conclusions are as certain as any based upon probable reasonings 

 can be. And they are so, simply because a very large experience 

 justifies us in believing that teeth of this particular form and 

 structure are invariably associated with the peculiar organisation 

 of sharks, and are never found in connection with other organisms. 

 Why this should be we are not at present in a position even to 

 imagine ; we must take the fact as an empirical law of animal 

 morphology, the reason of which may possibly be one day 

 found in the history of the evolution of the shark tribe, but for 

 which it is hopeless to seek for an explanation in ordinary 

 physiological reasonings. Every one practically acquainted with 

 paL-eontology is aware that it is not every tooth nor every bone 

 which enables us to form a judgment of the character of the 

 animal to vhich it belonged, and that it is possible to possess 

 many teeth, and even a large portion of the skeleton of an 

 extinct animal, and yet be unable to reconstruct its skull or its 



^.."De Solido intra Solidum," p 5. — " Dato corporecerta figurapraeditoet 

 juxta leges naturse producto, in ipso corpora argumenta invenire locum et 

 modum productionis detegentia." 



- " Corpora sibi invicem omnino similia simili etiammodoproductasunt." 



limbs. It is only when the tooth or bone presents peculiarities 

 which we know by previous experience to be characteristic of a 

 certain group that we can safely predict that the fossil belonged 

 to an animal of the same group. Any one who finds a cow's 

 grinder may be perfectly sure that it belonged to an animal 

 which had two complete toes on each foot, and ruminated ; any 

 one who finds a horse's grinder may be as sure that it had one 

 complete toe on each foot and did not ruminate ; but, if 

 ruminants and horses were extinct animals of which nothing but 

 the grinders had ever been discovered, no amount of physiological 

 reasoning could have enabled us to reconstruct either animal, still 

 less to have divined the wide differences between the two. Cuvier, 

 in the " Discours sur les Revolutions de la Surface du Globe," 

 strangely credits himself, and has ever since been credited by 

 others, with the invention of a new method of palaeontological 

 research. But if you will turn to the " Kecherches sur les Ossemens 

 Fossiles" and watch Cuvier, not speculating, but working, you 

 will find that his method is neither more nor less than that of 

 Steno. If he was able to make his famous prophecy from the 

 jaw which lay upon the surface of a block of stone to the pelvis 

 of the same animal which lay hidden in it, it was not because 

 either he, or any one else, knew, or knows, why a certain form 

 of jaw is, as a rule, constantly accompanied by the presence of 

 marsupial bones — but simply because experience has shown that 

 these two structures are co-ordinated. 



The settlement of the nature of fossils led at once to the next 

 advance of palaeontology — viz., its application to the deciphering 

 of the history of the earth. When it was admitted that fossils 

 are remains of animals and plants, it followed that, in so far as 

 they resemble terrestrial or freshwater animals and plants, they 

 are evidences of the existence of land or fresh water, and. 

 in so far as they resemble marine organisms, they are evidence.<: 

 of the existence of the sea at the time at which they were parts 

 of actually living animals and plants. Moreover, in the absence 

 of evidence to the contrarj-, it must be admitted that the ter- 

 restrial or the marine organisms implied the existence of land or 

 sea at the place in which they were found while they were ye 

 living. In fact, such conclusions were immediately drawn by 

 everybody, from the time of Xenophancs donmwards, who 

 believed that fossils were really organic remains. Steno discusses 

 their value as evidence of repeated alteration of marine and 

 terrestrial conditions upon the soil of Tuscany in a manner 

 worthy of a modern geologist. The speculations of De Maillet 

 in the beginning of the eighteenth century turn upon fossils, 

 and Buffon follows him very closely in those two remarkable 

 works, the " Theorie de la Terre" and the " Epoques de la 

 Nature," with which he commenced and ended his career as 

 a naturalist. 



The opening sentences of the " Epoques de la Nature" show 

 us how fully Buffon recognised the analogy of geological with 

 archa;ological inquiries. "As in civil history we consult deeds, 

 seek for coins, or decipher antique inscrijitions in order to deter- 

 mine the epochs of human revolutions and fix the date of moral 

 events ; so, in natural history, we must search the archives of 

 the world, recover old monuments from tlie bowels of the earth, 

 collect their fragmentary remains, and gather into one body of 

 evidence all the signs of physical change which may enable us 

 to look back upon the different ages of nature. It is our only 

 means of fixing some points in the immensity of space and of 

 setting a certain number of \\ayraarks along the eternal path 

 of time." 



Buffon enumerates five classes of these monuments of the past 

 history of the earth, and they are all facts of palseontologj'. In 

 the first place, he says, shells and other marine productions are 

 found all over the surface and in the interior of the dry land ; 

 and all calcareous rocks are made up of their remains. Secondly, 

 a great many of these shells which are found in Europe are not now 

 to be met with in the adjacent seas ; and, in the slates and other 

 deep-seated deposits, there are remains of fishes and of plants 

 of which no species now exist in our latitudes, and which 

 are either extinct or exist only in more northern climates. 

 Thirdly, in Siberia and in other northern regions of Europe 

 and of Asia, bones and teeth of ele hants, rhinoceroses, and 

 hippopotamuses occur in such numbers that these animals must 

 once have lived and multiplied in those regions, although at the 

 present day they are confined to southern climates. The de- 

 posits in which these remains are found are superficial, while 

 those which contain shells and other marine remains lie much 

 deeper. Fourthly, tusks and bones of elephants and hippo- 

 potamuses are found not only in the northern regions of the 



