330 ^Journal of Comparative Neurology and Psychology. 



that the toxic effects of electrolytes are due to chemical reactions and equilibrium 

 conditions and not to the electric charges of the ions. 



That the present stage of our knowledge of the chemistry of living matter is any- 

 thing but satisfactory could hardly be more clearly indicated than by the following 

 sentence from the pen of this enthusiastic seeker for physical-chemical descriptions 

 of vital phenomena: "It appears. . . that by the word'stimulation' wemean a 



process which is unknown to us, which, however, seems to consist in the 



substitution of Na- or K-iors for Ca, or vice versa, in some colloidal (proteid or 

 lipoid) compound of the muscle or nerve, whereby some physical qualities of the 

 colloidal substances are changed"(p- 105). 1 his sentence and many like it proves 

 that he who at present attempts to describe life phenomena in terms of chemical 

 processes must necessarily speculate as to the proper filling for numerous gaps in 

 his descriptions. 



In the lecture on heliotropism, we find for the most part the facts, as well as 

 the explanatory theory, which the author has discussed in his several papers on re- 

 actions to light. 1 he lecture has the striking merit of stating clearly and in readable 

 form certain of the most important facts thus far discovered in this field. 



A later lecture gives an equally lucid restatement of the author's orientation 

 theory. From one point of view it is rather surprising that Loeb did not give more 

 attention to facts, apparently not in accord with his theory, that have been brought 

 to light by other investigators. In several of this series of lectures he has noted 

 briefly the results of the work of a considerable number of investigators, but in this 

 particular field it seems as if he were clinging to his past rather than moving for- 

 ward either with or in advance of the progress of research. In this lecture on the 

 tropisms a sentence occurs which seems to contain one word too many: "I have 

 repeatedly pointed out that it is superfluous, and often indirect contradiction tothe 

 facts, to assume the existence of human sensations in lower animals, and to put 

 these hypothetical sensations as a necessary link between the external stimulus and 

 its motor effect" (p. 146). If the author really means to use the word human, it 

 would seem that his statement is superfluous. This is a trivial matter apparently, 

 merely a word more or less! yet if it is not a typographical error it suggests a lack 

 of attention to distinctions which is disastrous for the progress of science. 



The interesting materials of the lectures on fertilization, heredity and regenera- 

 tion might be discussed more appropriately in a journal of experimental biology 

 than in this Journal. It should be noted, however, that they present a considerable 

 number of recently discovered facts in these fields, and point out in a stimulating 

 way further possibilities of progress. 



In criticising Loeb's book, we should not fail to consider the occasion of the 

 preparation of these lectures. They were delivered in Columbia University. As 

 a result of adaptation to this end they lack exhaustiveness and are somewhat 

 dogmatic in statement. 



ROBERT M. YERKES. 



