April 26, 1906] 



N.A TCJRE 



62 s 



gained by their larger brains ? Why has there been this selection 

 in all lines of animal descent of increased cerebral tissue ? 



I think we gain a key to the answer to this question by a 

 consideration of the differences of cerebral quality between man 

 and apes. Man is born with fewer ready-made tricks of the 

 nerve centres — those performances of an inherited nervous 

 mechanism so often called by the ill-defined term "instincts" — 

 than are the monkeys or any other animal. Correlated with 

 this absence of inherited ready-made mechanism, man has a 

 greater capacity for developing in the course of his individual 

 growth similar nervous mechanisms (similar to but not identical 

 with those of "instinct") than any other animal. He has a 

 greater capacity for " learning " and storing his individual 

 experience, so as to take the place of the more general inherited 

 brain-mechanisms of lower mammals. Obviously such brain- 

 mechanisms as the individual thus develops (habits, judgments, 

 &c.) are of greater value in the struggle for existence than are 

 the less specially-fitted instinctive in-born mechanisms of a race, 

 species or genus. The power of being educated — " educabiliiy " 

 as we may term it — ^is what man possesses in excess as compared 

 with the apes. I think we are justified in forming the hypothesis 

 that it is this " educability '' which is the correlative of the 

 increased size of the cerebrum. If this hypothesis be correct — 

 then we may conclude that in all classes of Vertebrata and even 

 in many Invertebrata — there is and has been a continual tend 

 ency to substitute "educability" for mere inherited brain- 

 mechanisms or instincts, and that this requires increased volume 

 of cerebral substance. A mere spoonful of cerebral tissue is 

 sufficient to carry abundant and highly efficient instinctive 

 mechanisms from generation to generation ; but for the more 

 valuable capacity of elaborating new brain-mechanisms in the 

 individual as the result of the individual's experience of surround- 

 ing conditions, a very much larger volume of cerebral tissue is 

 needed. 



Thus it seems probable that " educability " has increased in 

 those Mammalia which have survived. The ancient forms with 

 small brains though excellent " automata " had to give place, by 

 natural selection in the struggle for existence, to the gradually 

 increasing brains with their greater power of mental adaptation 

 to the changing and varied conditions of life : until in man an 

 (^rganism has been developed which, though differing but little 

 in bodily structure from the monkey, has an amount of cerebral 

 tissue and a capacity for ediication which indicates an enormous 

 period of gradual development during which, not the general 

 structure, but the organ of "educability," the cerebrum, was 

 almost solely the objective of selection. 



Two lines of speculation and inquiry are strongly affected by 

 the hypothesis thus sketched. 



Firstly, as to the general laws of progressive development of 

 bodily structure by the operation of natural selection — is it not 

 probable that in various .groups of animals, just as in the case of 

 man among the Primates, the operation of natural selection on 

 bodily structure (limbs, teeth, hair, horns, &c.) must have been 

 checked, or even altogether suspended, by. the transference of 

 selection to the all-important organ of educability, the cerebrum 

 or corresponding nerve-centres ? Adaptation by means of the 

 mental powers must take the ■ place of adaptation of bodily 

 structures. The educable animal leaves the ground and learns 

 to climb trees in order to gain its food, whilst in another race the 

 slower process of alteration of bodily form is evolving a long 

 neck to reach the green twigs, or a ponderous strength of limb 

 which can pull trees to the ground. Many similar cases will 

 .''Uggest themselves to the reader in which, even in lower animals, 

 the capacity of learning by experience must (as it were) defeat 

 and turn from its route the otherwise triumphant transformation 

 of bodily structure. 



Secondly, the question of the transmission of acquired char- 

 acters is largely touched by these speculations. The character 

 which we describe as " educability" can be transmitted, it is a 

 congenital character. But the results of education can not be 

 transmitted. In each generation . they have to be acquired 

 afresh, and with increased "educability " they are more readily 

 acquired and a larger variety of them. On the other hand, the 

 nerve-mechanisms of instincts are transmitted, and owe their 

 inferiority as compared with the results of education to the very 

 fact that they are not acquired by the individual in relation to 

 his particular needs, but have arisen by selection of congenital 

 variation in a long series of preceding generations. 



To a large extent the two series of brain-mechanisms, the 

 " instinctive " and the " individually acquired," are in opposition 



^^' '59', VOL. 61] 



to one another. Congenital brain-mechanisms may prevent the 

 education of the brain and the development of new mechanisms 

 specially fitted to the special conditions of life. To the educable 

 animal— the less there is of specialised mechanism transmitted 

 by heredity, the better. The loss of instinct is what permits 

 and necessitates the education of the receptive brain. 



We are thus led to view that it is hardly possible for a theory 

 to be further from the truth than that espoused by George H. 

 Lewes and adopted by George Romanes, namely that instincts 

 are due to " lapsed " intelligence. The fact is that there is no 

 community between the mechanisms of instinct and the mechan- 

 isms of intelligence, and that the latter are later in the history 

 of the development of the brain than the former, and can only 

 develop in proportion as the former become feeble and defective. 



These few lines— for the abruptness of which I apologise — 

 will, I trust, serve to show the interesting nature of the sjjecula- 

 tions connected with the significance of the size of the cerebrun* 

 in various Mammalia and other animals. Some of the suggestions 

 obtained from a consideration of the subject will, if carried out 

 in detail, be found of first-rate importance in building up the 

 science of comparative psychology. 



ZONES IN THE CHALK. 



'X'lIE philosophical observations on the genus Micrastery 

 -*■ which were communicated by Dr. A. W. Rowe to the 

 Geological Society in 1899, have been followed by the publica- 

 tion of his special researches on the zones of the white chalk on 

 the coasts of Kent and Sussex. This second most valuable 

 essay has been communicated to the Geologists' Association 

 {Proceedings, vol. xvi. March 1900), who are to be congratu- 

 lated on having such an addition to their published works. The 

 paper follows along the lines so ably sketched out more than 

 twenty years ago by Dr. Barrois ; and Dr. Rowe, in nearly all 

 cases, confirms the previous zonal distinctions and largely in- 

 creases our knowledge. He shows how invaluable it is to 

 collect stage by stage, and to pay the closest attention to the 

 minute changes which the fossils, and particularly the Micrasters» 

 undergo The paper is essentially a zoological one, invaluable 

 in indicating the succession of life, and as a contribution towards 

 the genesis of species. 



The ordinary subdivisions of lower, middle and upper chalk,, 

 which are important when we deal with purely geological pro- 

 blems, are not here dealt with ; but the author, who apparently 

 takes little interest in stratigraphy apart from fossils, admits that 

 " we can generally recognise the zones from the ap[)earance of. 

 the chalk alone, and that the fossils act as confirmatory evi- 

 dence." This, indeed, is the experience of those who have 

 worked at zones, and it is only by utilising properly all the 

 evidence that satisfactory results can be obtained, i Litholo-. 

 gical evidence, often invaluable, is essentially local ; the palseon-. 

 lological evidence, so ably and exhaustively dealt with by Dr. 

 Rowe, is clear and uniform throughout the areas with which he, 

 deals The fossils, as he remarks, "never fail us," — that is tot 

 say, when you find them, their testimony is safe after the expe- 

 rience he has gained. He has been fortunate in having such an 

 excellent series of sections to work at, and these are well de- 

 picted in two folding plates, drawn by Mr. C. Davies Sher-; 

 born. Inland, of course, the observer has only a pit-section or 

 road-cutting here and there to act as a guide to the zonal divi- 

 sions, but no doubt with the aid of the clear descriptions given 

 by Dr. Rowe, and of the ascertained thicknesses of the several 

 zones, it might be possible and even desirable to trace inland 

 their approximate boundaries, if any useful purpose were thereby 

 gained. In any case. Dr. Rowe's work will be appreciated alike 

 by field-geologists and palceontologists. Prof. J. W. Gregory 

 describes a new Echinoderm, and Dr. F. L. Kitchin describes a, 

 new species of Terebratnhna from the chalk. 



UNi VERS I lY AND ED UC A TIONA L 

 INTELLIGENCE. 

 Cambridge.— Mr. R. H. Yapp has been appointed assistant 

 curator of the Herbarium under Prof. Marshall Ward. 



Prof. Clifford AUbutt was on April 23 appointed physician to 

 Addenbrooke's Hospital, in accordance with the recent agree- 

 ment between the University and the governors. 



Dr. Adami and Mr. de Soyres have been appointed delegates 



