194 NATURE STUDY REVIEW [9:6— Sept., 1913 



the problem of animal intelligence. Mr. Mills believes that the 

 beaver is an animal with a good deal of intelligence and cites his 

 skill in building the dams, dredging the canals, and dealing with 

 the general engineering problems, as conclusive evidence of his 

 very intelligent work. Possibly some of his evidence is open to 

 criticism. For instance he cites the case of an aged beaver who 

 "waddled near an aspen, gazed into its top for a few seconds, 

 then moved away and started to fell a five inch aspen. The tree 

 which he refused to begin work on," he tells us, "was entangled 

 at the top so that it would not have fallen even if the beaver had 

 cut through the trunk." On page eight, however, in discussing 

 the senses of the beaver he says "The eyes are weak." One 

 wonders if an animal with poor sight would see the entangled 

 branches. In another case he cites an instance of a young beaver 

 undertaking to cut down a tree upon which another beaver had 

 been working. Instead of taking advantage of the cut already 

 made he began work some four inches below the cut and finished 

 the job without utilizing the work already done. It would seem 

 difficult, however, to explain many of the actions that Mr. Mills 

 describes, especially the construction of canals, without granting 

 to the beaver a very high degree of animal intelligence. 



The Mechanistic Conception of Life, Biological Essays by Jacques 

 Loeb, 232 pages. The University of Chicago Press, $1.50. 



Dr. Loeb has for many years been known as one of the foremost 

 champions of the idea that life phenomena are reducible to chemical 

 and mechanical explanations; in his words, "that the sum of all 

 life phenomena can be unequivocally explained in physical and 

 chemical terms." This book is an attempt to indicate the pro- 

 gress that we have made in such an explanation. He himself 

 was the first investigator to demonstrate the possibility of starting 

 up the development of the egg by chemical stimuli instead of the 

 customary introduction of the sperm, and quite a little of the book 

 is devoted to a description of the methods used to accomplish this 

 and to the inferences from such work. He has also done a good 

 deal of work on the reactions of animals to such stirauli as light, 

 heat, and electric currents, and he points out how many of the life 

 phenomena are to be explained as reactions to these stimuli, not 

 only showing that there are such reactions, but explaining in very 

 plausible ways the manner in which these forces act upon the 



