18 



SCIENCE, 



[Vol. IV., No. 74. 



discovers memory of a low order among the 

 gastropods ; experiments with the echino- 

 derms and higher crustaceans having, up to this 

 time, given rather negative results. The latter 

 fact is the more surprising ; because among 

 some of the terrestrial arthropods — the ants, 

 bees, and wasps — this faculty is so wonderfully 

 developed. Memory of the higher kind, which 

 depends upon the association of ideas by 

 similarity, is met with among the fish and 

 batrachians. This involves another faculty ; 

 nam el j', perception. Differing from Spencer 

 in man} T particulars, and showing less con- 

 fidence in himself as to the rise of perception 

 than at other points, the author in general 

 regards it as the faculty of cognition, and finds 

 clear evidence of it among the insects, reach- 

 ing the general conclusion that reflex action 

 and perception advance together. Imagination 

 is stated to rise step by step with memory 

 and perception among the mollusks, insects, 

 spiders, crustaceans ; and the doubting reader 

 is referred to the actual observations in ' Animal 

 intelligence ' which sustain these conclusions. 

 As to the more complex mental powers, pro- 

 ceeding in the same line of argument, the 

 author discovers reason, with a knowledge of 

 the relation between means and end, among 

 the bees and wasps ; in this order he also 

 observes communication of ideas ; understand- 

 ing of words, and dreaming, are found among 

 the birds ; tools are intelligently used by 

 monkeys and elephants ; an indefinite sense 

 of morality is seen among dogs and anthro- 

 poid apes. The discussion of conscience, voli- 

 tion, and abstraction, is reserved for the last 

 volume. The various approximate levels at 

 which the signs of the emotions, the will, and 

 the intellect appear, are presented in a large 

 diagram, in which the faculties branching out 

 from a single stem, neurility, are seen in a 

 condensed view of the entire system. 



Fully one-half of ' Mental evolution in ani- 

 mals ' is devoted to the subject of instinct ; and 

 as it is treated with the utmost fulness and clear- 

 ness, with a critical discussion of the theories 

 of different writers, it forms an invaluable and 

 standard contribution to this much mooted 

 subject. In general, supporting the theo^ of 

 Darwin in opposition to the contradictory 

 views of Lewes and Spencer, 1 it is shown that 

 the origin of instincts ma} 7 be either primary 

 or secondary ; that is to say, — 



"Instincts may arise either by natural selection 

 fixing on purposeless habits which chance to be 



1 In his Principles of psychology. This work was written 

 before the publication of the Origin of species. Mr. Spencer 

 now admits the wide influence of natural selection. 



profitable, so converting these habits into instincts 

 (primary), without intelligence ever being concerned 

 in the process; or by habits originally intelligent be- 

 coming by repetition automatic (secondary)." 



While either of these causes may work alone, 

 3'et frequently in co-operation they evolve in- 

 stinct more rapidly by blended origin. In- 

 stinct is accordingly defined as " reflex action 

 into which there is imported the element of con- 

 sciousness ; " and the point is abby sustained, 

 that Spencer's derivation of instinctive from 

 reflex actions merely, is inadequate for the 

 higher animals, while Lewes's theory of the 

 ' intelligence ' origin is inadequate to explain 

 the instincts of the lower animals. Darwin's 

 essay on instinct, part of which only appeared 

 in the 'Origin of species,' is published as an 

 appendix to this volume. The author ac- 

 knowledges his indebtedness to this, as well as 

 to many manuscript notes left him hy the great 

 naturalist. 



An outline has been given of these unusually 

 interesting works ; and there is little space left 

 for extended criticism, although at many points 

 it is richly deserved. We find, among other 

 defects, that the candor of the author's preface 

 is not sustained throughout. He disclaims the 

 discussion of all philosophical questions, such 

 as the causal relations between mind and 

 matter, as apart from the objects of the book ; 

 yet, at several rough places where he feels called 

 upon to explain the origin of faculties, he does 

 it in terms of nerve fibres and cells. For ex- 

 ample : in the origin of consciousness we find 

 him groping after Spencer, and, with some 

 hesitation, deriving this faculty from 'gan- 

 glionic friction ; ' while at another turn he 

 reverses the causal relation, since it is con- 

 venient to do so, and suggests a psychical cause 

 for some material change. Discussing the 

 origin of nerve-fibres, he again quotes Spencer ; 

 although Balfour, in his address before the 

 British association in 1880, gave the whole 

 weight of his authority against Spencer's theo- 

 retical views. The accounts given of the evo- 

 lution of the first germs of mind and nerves 

 are necessarily obscure and assailable. It is 

 true that pure speculation is unavoidable in 

 such an intangible sphere of inquiry ; but the 

 intrinsic merits of the argument are dimmed, 

 and we believe the truth is delayed, when the 

 reader is so often left in doubt as to where the 

 author's observation ceases and his imagination 

 begins. As before stated, it is not the facts 

 of actual observation brought forward, but the 

 character of the inferences which are drawn 

 from these facts, which will arouse controvers} T . 



The American edition of ' Mental evolution ' 



