262 



NATURE 



[Feb. 5, 1874 



Barrande and the author of the article have restricted their re- 

 marks almost entirely to the trilobites, I will only ask to be al- 

 lowed spice to reply to the facts stated with regard to these 

 forms of life. Trilobites have now been discovered as low 

 down as 4,000 ft. in these red and green rocks at St. David's, 

 that is, in the very earliest fauna known, and amongst them are 

 forms hitherto not discovered in any other country ; still 

 if we are to believe with some that we are here near the 

 beginning of life on the globe, or even of trilobitic life, we can 

 expect but little evidence to support or to disprove Darwinism. 

 For, considering the frequent changes in the sea bottom 

 which must have taken place at this period, to produce at 

 one time a shingle, then a sand or grit, and then a tine muddy 

 deposit, and such beds freciuently repeated, we cannot possibly 

 expect that during all these physical changes an unbroken record 

 of these forms should be preserved to us. No, rather we should 

 expect to find that the necessary migrations would produce al- 

 terations in the forms, and that they should now and again return 

 modified and altered in proportion to the time wliich had inter- 

 vened and the circumstances which surrounded them. And this is 

 realywhat we do find, and which is apparent at once to the 

 palceontologist, who is prepared to allow and to recognise in 

 these very marked physical changes a controlling influence 

 capable of greatly affecting the life of the period. Again, can 

 any one really believe, when thinking of the enormous time 

 which must have elapsed during the accumulation of the great 

 Laurentian scries, and possibly of other series previous and 

 succeeding, all antecedent to the time when the Cambrian 

 fauna made its appearance, that the seas in which these were de- 

 posited were entirely barren of life ? Surely not ; therefore, why so 

 readily jump at concIu>ions when there is so much room for doubt ? 

 Again, this Cambrian fauna is not without evidence in favour of 

 evolution. Trilobites we know develope by increase of the 

 body segments, and therefore M. Barrande says that the earliest 

 trilobites should have the smallest numlicr of segments in the 

 thorax — " but that those of the primordial fauna are generally 

 characterised by the opposite condition, while the number is 

 less in those of the succeeding faunas." Now it does not seem 

 to have occurred to M. Barrande that trilobites show every indi- 

 cation of having culminated at or about this period, that they had 

 attained their maximum size and development, and that from 

 this tmie they seem to have gradually diminished in size, and to 

 have degenerated, doubtless much in the order in which they 

 had previously progressed. This will explain also why the 

 number of segments should, as he says, diminish in number in 

 the genera of succeeding faunas. One of the very earliest 

 trilobites we know of is the little A»Hosi!is. It is also the 

 simplest and apparently the most rudimentary of the group. It 

 has no eyes, only Iao segments to the thorax, and usually an ill- 

 defined glabella. In tracing a species of Paradoxides from the 

 earliest stage upwards, I was struck with the very great resem- 

 blance which, at an early stage, it had to the little Agnostiis. 

 The glabella was indistinct, and much shorter in proportion to 

 the length of the 'head than in the fully grown specimen, and 

 the eye very faint, scarcely marked out, and the outline of 

 the head more evenly rounded, with scarcely any indi- 

 cation of spines. Before the discovery of the Cambrian 

 fauna at St. David's, no genus of trilobites had been 

 found with four segments to the thorax, therefore we had 

 to jump from one with two to one with six, as in 

 Triniicleus or Ampyx. Now, however, since the discovery of 

 Mhrodiscus with four segments, the gap has been filled up, and 

 the genu=, unfortunately for those holding M. B.itrande's 

 views, appears in our earliest fauna, and where the evolu- 

 tionist would be most inclined to look for it. It is also a 

 most interesting and instructive genus. It is somewhat 

 larger than Ai;>wst':s, but like it, has no eye-. The glabella is 

 better formed, more distinctly marked off from the cheeks, and 

 instead of being irregularly grooved, as is usually the case with 

 Ai;iiosliis, it is furrowed regularly as in an advanced stage in the 

 development of /"i^v/i/y.v/r/tj. In the caudal portion the axis is 

 partly divided into segments, and in one species the lateral lobes 

 are slightly grooved as if into rudimentary pleur;-e. It is very 

 plentilul in the beds at St. David's, and since lis discovery there, 

 species have also been found in Canada and elsewhere. 



From this stage furms have been found to represent every step 

 in development as to the number of segments, and indeed often 

 to show marked stages in other pans. Anopolcniis is really a 

 Paradoxides with enormous eyes, reaching to tlie hinder margin, 

 and with several of the hinder pleurce consolidated together to 



form a large spinous pygidium. Another Paradoxides has the 

 eyes nearly as large as Anopoleiiits, but with a few more segments 

 to the thorax, and a smaller pygidium. Other species show 

 various gradations in the eyes and in the pygidium until we attain 

 to P. Dai'idis, which has small eyes, a small pygidium, and the 

 greatest number of thoracic segments. Indeed there are forms 

 to represent almost every stage, and there can I think be no 

 doubt that in the fauna of the Tremadoc group, which is sepa- 

 rated from the earlier Cambiian by several thousand (eet of 

 deposits indicating a j^eriod of vety shallow water in which large 

 brachiopods and phyllopod crustaceans were the prevailing forms 

 of life, we witness a return to very much the same conditions as 

 existed in the earlier Cambrian periods, and with these condi- 

 tions a fauna retaining a marked likeness to the earlier one, and 

 in which the earlier types are almost reproduced, though 

 of course greatly changed during their previous migrations. The 

 Niobe^) recently found in the Tremadoc rocks is truly a degraded 

 Paradoxides, retaining the glabella and head spines, but with 

 the rings of the thorax, excepting eight, consolidated together to 

 form an enormous tail. Instead therefore of having here, as 

 stated by M. Barrande, "a very important discord between 

 Darwinism and facts," we find in tnese early faunas facts strongly 

 favouring such a theory, and in support of evolution. 

 Hendon, Jan. 27 IIexry Hicks 



Accord i ng toanotice in N.^tu re, vol. ix. p. 22S, a distinguished 

 continental naturalist finds an important discordance between 

 Darwinism and certain facts connected with Trilobites and other 

 fossil crustaceans. But his argummt appears to be based on an 

 assumption that we are acquainted with a "primordial fauna," 

 that we are justified in dating the beginnings of life at or near 

 some known geological period. This, however, the whole his- 

 tory of geology ought to make us less and less inclined to believe. 

 It is one of those assumptions, essentially based on ignorance, 

 on which so little dependence can rightly be placed. We have 

 no right to call any fauna the earliest, merely because, as it hap- 

 pens, we know of none earlier. 



A point is made of the fact that the earlier known Trilobites 

 have more segments than the later, while individual Trilobites, 

 as they develope, increase in number of their body segments. 

 It may be granted at once that in this case the development of 

 the individual is not an accurate picture of the jiast development 

 of the species. But Fritz Midler has long ago shown that we could 

 not, on principles of Darwinism, expect it always to be so ; and 

 surely, if Trilobites have been gradually developed rather than 

 abruptly created, there must have been Trilobites with ycTc/ before 

 there were Trilobites with many segments, so that after all, the 

 development of the individual will carry us back to an early stage 

 in the history of the family. It could scarcely be expected to 

 give us all the alternations and complications which that history 

 may have presented in its whole course. 



Those who on other grounds accept the theory of evolution, 

 far from finding any obstacle to it in the large number of genera 

 of .Silurian Trilobites, will consider the largeness of that number 

 clear evidence that life in general, andTrilobite life in particular, 

 must have flourished on the globe for a very long period prior 

 to the Silurian age. 



The argument that we do not find connecting links between 

 dilTerent genera has little immediate force. It must await the 

 verdict of time and further investigation. Of 252 species o 

 Trilobites, 6l are assigned to England. The true reading 

 of this piece of statistics must surely be that that which great 

 research has done for a small area may be equalled, and far 

 surpassed, when as close a scrutiny is applied to the whole 

 available surface. If no gaps between species, and genera, and 

 orders are filled by the results of such a search, then it will be 

 time to say that we have "an important discord between Dar- 

 winism and facts. " 



Torquay, Jan, 27 TuOM.VS R. R, SxEliBlNG 



Perception in Lower Animals 



I RELATE the following, as it has some bearing on a question 

 lately ventilated in N.vrt'RE. 



A friend and mysell were watching on one occasion the actions 

 of two half-bred Persian cats on seeing for the first time a freshly 

 caught cobra, which had been placed in a wire-gauze covered 

 box near the verandah. First or all one of the cats, a black one, 

 stalked carefully up to the box in which the snake was keeping 

 up a perpetual "swearing," with extended hood, and after a 



