Feb. 7, 1884] 



NATURE 



m 



intelligence. In the first place, what the writer calls 

 primary instincts, including those of many low animals 

 and certain instincts of higher animals, e.g. incubation, 

 arise by the action of the first cause. This is proved by 

 the fact that purposeless habits, tricks of manner, e.g. 

 the trick of barking round a carriage showing itself in 

 certain varieties of dogs, occur and are inherited. In the 

 second place, secondary instincts, including many of those 

 of the higher animals, eg. dread and shunning of man, or 

 other enemies, were originally intelligent actions, and 

 illustrate the principle of habit or lapsed intelligence. 

 This pr iposition, again, is established by showing first, 

 that " intelligent adjustments when frequently performed 

 become automatic in the individual, and next that they 

 are inherited till they become automatic habits in the 

 race," eg. in the tendency of certain breeds of dogs to 

 " beg." 



In combining both these principles in his theory of 

 instinct, Mr. Romanes follows his master, Mr. Darwin, 

 and he has derived much assistance from the valuable 

 essay on instinct by that writer, which was written for the 

 " Origin of Species," but, having been withheld from that 

 publication for want of space, now appears for the first time 

 as an appendix to Mr. Romanes' volume. But the author 

 has elaborated the theory sketched out by Mr. Darwin. 

 More particularly he has illustrated at great length how 

 the two causes may combine. He shosvs how on the one 

 hand, primary instincts may come to be put to better 

 uses by intelligence, and, on the other hand, secondary 

 instincts may be modified and put to better uses by 

 natural selection. The effects of domestication illustrate 

 most clearly this conjoint action of the two principles. 

 With respect to the comparative importance of the two 

 causes, Mr. Romanes seems inclined to look at natural 

 selection as the chief agency, intelligent adjustment 

 being regarded as an auxiliary agency, the chief function 

 of which is to supply to the controlling principle of 

 natural selection an additional class of variations which are 

 from the first adaptive. Mr. Romanes supports his theory 

 by a cumulative chain of argument of very great strength, 

 and he orders the successive steps of it in such a way as 

 to make the reader feel its full force. His main positions 

 seem to us unassailable. The only point we feel inclined 

 to criticise is the limitation of the action of intelligence 

 in the instincts of animals low down in the scale The 

 author appears to argue on general grounds that these 

 must to a large extent be due to the working of natural 

 selection. But the facts of intelligent modification of 

 instinctive actions cited by him, eg. in the case of the 

 constructive actions of bees, &c., appear to show that the 

 animals concerned possess a considerable measure of 

 genuine sagacity. And while it is no doubt difficult, as 

 the author remarks (p. 191), to attribute to an animal so 

 low down in the scale as the larva of the caddice fly a 

 power of consciously reasoning, it seems, on the other 

 hand, hard to understand how, by the mere play of natu- 

 ral selection unaided by any rudiment of conscious dis- 

 crimination and adaptation of means to ends, this little 

 creature could have acquired the habit of either lighten- 

 ing its floating case by attaching a leaf to it or weighting 

 it by attaching a small stone according as it becomes too 

 heavy or too light. But the author shows himself so 

 completely the master of his subject, that the reader feels 



disposed to accept his conclusions in the very few in- 

 stances in which his individual judgment leans the other 

 way. J.^MES Sully 



OUR BOOK SHELF 



An Introduction to the Study 0/ Heat. By J. Hamblin 



Smith, M.A. (London : Rivingtons, 1883.) 

 Though the author states in the preface that " he has 

 endeavoured in this book to explain the elementary facts 

 connected with the theory of heat so far as a knowledge 

 of them is required by the University of Cambridge in 

 the general examination for the ordinary B.A. degree," 

 it will be found that he has succeeded in producing a 

 book which is not only admirably adapted to help a stu- 

 dent who is preparing for this or any other elementary 

 examination, but which, from the simple nature of the 

 language and the clearness of the descriptions, may be 

 read with advantage by those who have no examination 

 to pass, but who may wish to understand something of 

 the science of heat for its own sake. 



The text is composed of short numbered paragraphs, 

 in each of which the author deals with one new fact only, 

 a plan eminently adapted to save the student confusion. 

 These paragraphs may be taken as model answers to 

 imaginary examination questions. 



Over two hundred questions are given on those parts 

 of the subject, such as expansion, calorimetry, conduct- 

 ivity and hygrometry, which admit of being put in simple 

 numerical form. Many of these are essentially exercises 

 in arithmetic, and must irresistibly remind the reader of 

 the unlikely questions which he used to have to answer at 

 school. In the questions on thermometers, for instance, 

 an observer seems to have noted the sums, differences, 

 products, &c., of the readings of every kind of thenno- 

 meter in his laboratory, without noticing what those read- 

 ings were, and then, when too late, to have met with the 

 necessity of finding from his observations the tempera- 

 tures which the instruments actually indicated. However, 

 though observations of such a kind are rarely made, the 

 exercises which they furnish will of necessity make those 

 who work them out absolutely familiar with the funda- 

 mental principles of the subject. C. V. B. 



LETTERS TO THE EDITOR 

 \The Editor does not kotd hhnselj responsible for opinions expressea 

 I'y his correspondents. Neither can he undertake to return, 

 or to correspond with the writers of, rejected manuscripts. 

 No notice is taken of anonymous cofurnunfcations. 

 [The Editor urgently requests correspondents to keep their letters 

 as short as possible. The pressure on his spact is so great 

 that it is impossible otherwise to insure the appearance even 

 of comii. unications containing interesting and novel facts.l 



The Ear a Barometer 



At ,t time when I frtquently went betv\ een Peterborough and 

 London by the Great Northern Railway express trains, I found 

 that the sudden compression of the air produced on entering a 

 tunnel was not only perceptible by the ear, but even unpleasant, 

 and that this unpleasant sensation remained till the open air was 

 reached, when it suddenly ceased. Of course it was natural to 

 .suppose that the noi.se was the primary cause, but I satisfied 

 myself that this had nothing to do with the effect, for on swal- 

 lowing after entering the tunnel the sensation ceased, but 

 recurred in the opposite sense on leaving the tunnel, when a 

 second operation of swallowing removed it. This showed clearly 

 that what was observed was real. 



As far as I remember there was, as measured by the sensation, 

 an increa'se of pressure, at first sudden, and then gradually rising 

 for a second or two on entering, and a corresponding gradual 

 and sudden decrease on leaving a tunnel. 



I did not at the time have the opportunity of taking an aneroid 

 with me to measure the amount of the compression, but intended 

 to try an air thermometer which I thought would be more 



