5 6z POPULAR SCIENCE MONTHLY. 



of these points. We would only further say that, while the book is spe- 

 cially intended for scholastic use, it is well adapted for general reading, and 

 that it could not be read carefully by any one without profit. 



Prof. Wesley Mills holds the opinion that in the present stage of the 

 study of animal life,* facts are much more desirable than theories. Experi- 

 ment and observation must go on for many years before generalizations will 

 be worth the making. Putting this belief into practice, he has bred and 

 reared a large number of animals, making most careful notes on their 

 physical and mental development, and furnishes in his book, resulting from 

 these studies, a contribution of unquestionable value to comparative psy- 

 chology. 



In his investigation of the habits of squirrels, he finds the red squirrel, 

 or chickaree, much more intelligent than the chipmunk. The latter is 

 easily trapped, but the former profits by experience and is rarely secured a 

 second time. These little creatures are also adepts in feigning. Two ex- 

 amples are cited in which squirrels apparently ill recovered rapidly when . 

 left alone and made their escape in vigorous fashion. Many instances of 

 animals shamming death are judged to be cases of catalepsy induced by ex- 

 cessive fear. The chickaree is also credited with some musical capacity, 

 one being observed, when excited, to utter tones that were birdlike ; 

 whence it is concluded "likely that throughout the order Rodentia a genu- 

 ine musical appreciation exists, and considerable ability in expressing states 

 of emotion by vocal forms." 



While experimenting with hibernating animals, Professor Mills kept a 

 woodchuck in confinement five years, and noted that it had a drowsy or 

 torpid period from November to April. Another specimen subjected to the 

 same conditions did not hibernate for an hour during the entire season. 

 Bats began to hibernate at 45° to 40° F., and were so affected by temperature 

 that they could be worked like a machine by varying it. The woodchuck, 

 however, was comparatively independent of heat and cold, but very sensitive 

 to storms. This is found to be true of many wild animals, that they ,l have 

 a delicate perception of meteorological conditions, making them wiser than 

 they know, for they act reflexly." 



Some records are given of cases of lethargy among human beings, and 

 in regard to these, as well as normal sleep and hibernation, it is suggested 

 that their conditioning and variability throw great light upon the evolution 

 of function. 



In order to observe closely the psychic development of young animals, 

 Professor Mills raised families of dogs, cats, chickens, rabbits, guinea-pigs, 

 and pigeons. The data obtained by him, given in the form of diaries with 

 comparisons and conclusions, constitute Part III, the larger half of the 

 book, unquestionably first in importance and interest. It is scarcely possible 

 to overvalue careful studies like these, undertaken not to justify theories, 

 but to bring to light whatever truths may be apprehended of the nature of 

 growth and connection of mind and body. 



The last division of the book contains the discussions on instinct by 

 Professors Mills, Lloyd Morgan, Baldwin, and others, first published in 

 Science. The beginning of the volume, devoted to a general considera- 



* The Nature and Development of Animal Intelligence. By Wesley Mills, F. R. S. C. N:w York : 

 The Macmillan Company. Pp. 307. Price, $2. 



