August 14, 1914;] 



SCIENCE 



245 



A chapter of especial interest to Americans 

 discusses " Tlie Causes of Genetic Variation," 

 for the work reviewed is to a considerable ex- 

 tent that of American biologists, who have 

 attempted to produce and claim to have suc- 

 ceeded in producing heritable variations under 

 controlled experimental conditions. The work 

 of Woltereck in Germany has shown, accord- 

 ing to Bateson, that the character of the food 

 supplied to a parthenogenetic Daphnia affects 

 the structure of her immediate offspring, but 

 the effect does not persist further into subse- 

 quent generations. Hence there is no perma- 

 nent racial influence. Tower, however, in 

 potato-beetles, and MacDougal in Raimannia 

 claim to have brought about permanent racial 

 changes, the one by altering the temperature 

 and humidity at which the parent beetles are 

 kept, the other by injecting certain salt solu- 

 tions into the ovaries of the parent plants. 

 Bateson points out that neither of these im- 

 portant results has been independently con- 

 firmed by experiment, though this has been 

 attempted by Oompton with negative results 

 in the case of Raimannia. After reviewing 

 Tower's two principal papers and pointing out 

 a number of inconsistencies, Bateson adds 



" The hesitation which I had come to feel 

 respecting these two publications of Tower's 

 has been, I confess, increased by the appear- 

 ance of a destructive criticism by Gortner who 

 has examined the parts of Chapter HI of 

 Tower's book in which he discusses at some 

 length the chemistry of the pigments in 

 Leptinotarsa and other animals. As Gortner 

 has shown, this discussion, though offered 

 with every show of confidence, exhibits such 

 elementary ignorance, both of the special sub- 

 ject and of chemistry in general, that it can 

 not be taken into serious consideration." 



Eegarding MacDougal's work he says, em- 

 phasizing the need of repeating the experiment 

 with Raimannia: 



" He [MacDougal] adds that he is making 

 similar experiments with some twenty genera; 

 l)ut what is more urgently needed is repeated 

 confirmation of the original observation. 

 When it has been shown that this mutation 



can be produced with any regularity from a 

 plant which does not otherwise produce it on 

 normal self-fertilization, the enquiry may be 

 profitably extended to other plants." 



The net result of Bateson's discussion of 

 the causes of genetic variation is negative. Wo 

 means of controlling genetic variation has, 

 he believes, yet been found. 



A chapter dealing with The Sterility of 

 Hybrids presents many interesting questions 

 without answering any of them satisfactorily. 

 Interspecific sterility is shown to be important 

 in keeping species distinct, and it is suggested 

 that in some cases at least it is connected with 

 unit character inheritance, but beyond this 

 point all is uncertainty. 



In his concluding remarks, Bateson empha- 

 sizes the present partial and incomplete state 

 of our knowledge of genetic problems and in 

 particular of what a species really is. He 

 expresses the conviction that it is not a mere 

 arbitrary group of organisms, though to the 

 systematists it can hardly be anything else. 

 " Their business," says Bateson, " is purely 

 that of the cataloguer, and beyond that they 

 can not go. They will serve science best by 

 giving names freely and by describing every- 

 thing to which their successors may possibly 

 want to refer, and generally by subdividing 

 their material into as many species as they 

 can induce any responsible society or journal 

 to publish. 



" As yet the genetic behavior of animals 

 and plants has only been sampled. When the 

 work has been done on a scale so large as to 

 provide generalizations, we may be in a posi- 

 tion to declare whether specific difference is or 

 is not a physiological reality." 



W. E. Castle 



Vorirdge uber Deszendenztheorie. Von Au- 

 gust Weismann. Dritte umgearbeitete Au- 

 flage. Jena, G. Fischer. 1913. Pp. xiT + 

 354, 3 pis., 137 figs, in text. 



Mendel's Principles of Heredity. By W. Bate- 

 son. Cambridge, Eng., Univ. Press, and 

 New York, G. P. Putnam's Sons. 1913. 

 3d Impression. Pp. xiv + 413, iUustr. 

 These two books deal with the two most im- 



