NA TURE 



[May 2, 1907 



for discussion by Mr. Standing, and also incline me to 

 suggest a modification ol my previously expressed views. 



The evidence afforded by the cranial casts is very 

 precise and unmistakable. One of them does not differ 

 in any essential feature, excepting size, from the form 

 exhibited by the brain in the living species of the genus 

 I^emur ; a second is an almost exact replica of the cranial 

 cast of Indris; and the third, so far from affording any 

 evidence of affinity to monkeys, presents highly specialised 

 features, which enable us to place the animal (and also 

 Nesopilhecus, Megaladapis, and possibly Chiromys) within 

 (he fringe of the Indrisina;. As these lemuroids are the 

 most diversely modified members of the most highly 

 specialised family of the Prosimia? — which means that they 

 are furthest removed from (and presumably have retained 

 least resemblance to) the very early and remote ancestor 

 from which both lemurs and apes could have sprung — it 

 follows that these, the most aberrant and outlying branches 

 of the prosimian phylum, are the least likely to supply 

 us with any evidence bearing on the relationship of 

 lemurs to apes ; and the facts elucidated by the actual 

 e.xamination of these specimens quite bear out this a priori 

 supposition. 



I am the more anxious to make my position absolutely 

 clear in regard to this matter for the reason that, some 

 four yeais ago (Linn. Soc. Journal — Zool., vol. .\xix., 

 p. K3), in protesting against Hubrecht's suggested exclusion 

 of all Prosimia^ (except Tarsius) from the Primates, I 

 may have unduly ininimised the differences in structure 

 that indicate the wide separation of the Lemuroidea and 

 the Anthropoidea. 



The organisation of every part of the body proclaims 

 the kinship of lemurs and monkeys, distant though it be; 

 this has been so often summarised (see Earle, " On the 

 Affinities of Tarsius," the American Naturalist, 1897, pp. 

 569 and 6S0) that it does not need repetition. I might 

 direct attention to the fact that the lemurs are the only 

 mammals that exhibit the true Sylvian fissure such as 

 we find in the Anthropoidea or Simite ; that the true 

 central (Rolando's) sulcus is present in Perodicticus and 

 in no non-Primate mammal, although there are distinct 

 evidences in many prosimian families of the tendency 

 toward the development of this caudal-limiting sulcus of 

 the motor area ; that the motor area presents histological 

 features like those of the lowlier monkeys, and has a 

 similar topographical distribution ; that the calcarine 

 sulcus and the distribution of the visual cortex (area 

 striata) conform essentially to the Primate type, although 

 in certain respects the structure of this cortex and its 

 relation to sulci more nearly resembles the condition found 

 in certain primitive Carnivora ; and that the organisation 

 of the other parts of the cerebral hemisphere and of the 

 brain-stem and cerebellum resembles that of the corre- 

 sponding parts of the brain in monkeys much more nearly 

 than that of the Carnivora and Edentata, in which there 

 are some analogies to the Prosimia;. 



But if the facts of cerebral anatomy establish the claim 

 of the Prosimian to be Included in the Primates, they afford 

 equally emphatic evidence of the sharp line of demarcation 

 between the diversely specialised suborders Lemuroidea 

 (Lemures) and Anthropoidea (SImi») and the degraded 

 rank of the former. In attempting to formulate the con- 

 trasts between these two suborders, Tarsius comes to 

 occupy such an enigmatical position that it must be put 

 into a category by itself, the suborder Tarsii (Gadow), 

 the other I-emuroidea then forming the suborder Lemures 

 (Hubrecht). 



The Lemures are macrosmatic. and (excluding Megala- 

 dapis) have a sessile olfactory bulb, whereas the Simije 

 are microsmatic, and have an elongated olfactorv peduncle. 

 Tarsius has a sessile olfactory bulb like the Lemures, and 

 in form exactly like that of the Galaginne and Lorisinrc, 

 but it is much smaller than that of any lemur, and at the 

 same time is bigger than that of a monkey. 



The cerebral hemisphere in the Simla? is prolonged 

 backward to cover the cerebellum, carrying with it a 

 diverticulum of the lateral ventricle to form a posterior 

 cornu, the walls of which are composed to a large extent 

 of very highly specialised striate cortex differing markedlv 

 in structure from the homologous area of other mammalian 

 NO. 1957, VOL. 76] 



orders. In Lemures the occipital prolongation is not so 

 extensive; there is no posterior cornu, and the cortex of 

 the area striata approximates in structure to that of the 

 Carnivora more nearly than to that of the apes. Ini 

 Tarsius the extent of the occipital pole and its form most! 

 nearly resemble the condition found in the brain of the| 

 Galaginse, but there is an extensive posterior cornu as i 

 the apes, and the structure of the area striata presents 

 marked contrast to that of the lemurs, and resembles that 

 found in Hapale and Cebus. 



In the lemurs the frontal, temporal, and parietall 

 association areas are much smaller than in monkeys. 



The lateral hemispheres of the cerebellum exhibit 

 much greater expansion in the Simise than in the Lemures,! 

 although there is a very close resemblance between the| 

 patterns exposed in mesial section in the two suborders. 



In many respects the structure of the brain in Tarsiusl 

 departs widely from that of all the other Primates, both , 

 Lemures and Simi;c. Most of these features, such as the 

 form and proportions of the corpus callosum and the 

 architecture of the cerebellum, are indicative of a very 

 primitive generalised condition, such as we find in the 

 insectivore Gymnura. 



All these considerations, and the mass of facts elucidated 

 by Burmeister, Turner, Hubrecht, Mivart, Leche, Eugen 

 Fischer, and the writer among many others, can, I think, 

 find a rational explanation only by admitting that the 

 Primates consist of three divergent phyla, which have all 

 departed in varying degrees and in different ways from 

 their original common ancestor, which must have been a 

 creature in many respects like Tarsius, but more macros- 

 matic, and possessed of a smaller and less highly specialised 

 visual cortex. G. Elliot S.\iitii. 



The School of Medicine, Cairo, .April 22. 



Radium and Geology. 



Two points of special interest have come to light in 

 recent investigations which I have made in connection 

 with this subject. 



(i) Typical rocks from the Simplon Tunnel contain 

 quantities of radium considerably in excess of the average 

 of igneous rocks. The Simplon rocks are altered sedi- 

 ments, for the most part, from Arch.Tean to Jura-Lias 

 age. There appears to be suflicient radium to account for 

 the excessive temperatures met with in boring the tunnel, 

 and the practical suggestion is allowable that engineers 

 will do well to estimate the distribution of this substance 

 before embarking on similar projects in the future. 



The investigation suggests that radium, accumulating 

 In great thicknesses of sedimentary deposits, may enter 

 as a factor in mountain building by raising the temperature 

 at the base of the accumulated mass. This would lead 

 to a lessened resistance to compressive stress and pressure 

 from beneath. In short, it will be for future Investigation 

 to explore how far radium (and uranium) in the surface 

 materials has proved a source of instability in geological 

 history, its transport by denudation being, in fact, not a 

 transport of matter only, but a convection of energy. 



(2) A sample of red clay from a depth of 2740 fathoms 

 in the North Atlantic contained sixteen times as much 

 radium as the average of igneous rocks as determined 

 by the Hon. R. J. Sirutt, and a specimen of globlgerina 

 ooze from .'i depth of nioo fathoms in the South Atlantic 

 about six times this average. These materials I owe to 

 the kindness of Sir John Murray. 



Here the question will arise, Whence all this radium? 

 Sir John Murray's cosmic dust, of course, at once comes 

 to mind, and, taking all the facts into account, I venture 

 to regard these results as further evidence in favour of 

 the extra-terrestrial origin of some portion of the radium 

 wo find upon the earth. 



The above results are obtained by measurement of the 

 emanation, with every precaution against error. 



The point as to what constituent of the oceanic de- 

 posits is responsible for the radium is under investigation. 



J. JOLV. 



Geological Laboratory, Trinity College. Dublin, 

 April 29. 



