February ig, 1920] 



NATURE 



655 



ception of sugar and amino-acids ; it suffices at 

 this stage if the student can differentiate the two 

 classes of compounds, for the subject-matter is 

 rather the origin and metabolism of carbon and 

 nitrogen in Nature, and the supply of energy in 

 the form of food. Food undergoes changes in the 

 body as the result of enzyme action ; the section 

 on the nature of enzyme action is scarcely long 

 enough, and reference must here be made to the 

 "Principles." Respiration and oxidation are, in 

 contrast, fully discussed. These two chapters are 

 the chief ones in the book. 



"Work — The Muscles and Stimulation — The 

 Senses " are the subject-matter of chaps, iii. 

 and iv. In the latter chapter there is a diagram- 

 matic representation of the mechanism of the 

 organ of Corti. Prof. Bayliss lays special stress 

 upon a student getting a clear idea, even if it 

 be erroneous, for it can be easily changed later, 

 and it is far better than conflicting views which 

 leave no impression. Chap. v. is a difficult 

 one on ".Adjustment — The Nervous System," 

 and requires close attention to the text. 



Chap. vi. is on "The Transport of Materials — 

 The Vascular System." Here, again, we get an 

 illuminating and fascinating description, while 

 chap, vii., on "Growth and Reproduction," shows 

 how the author himself has thought out his 

 subject for explanation to the student. 



Each chapter has a corresponding section on 

 laboratory work, in which there is frequently 

 some further explanation. The practical exercises 

 illustrate the text, and are of varying difficulty. 

 Many have been specially devised, while others are 

 adaptations of existing experiments in physical 

 chemistry or physiology. The value of experi- 

 ments is very great, for science becomes a 

 reality only in these circumstances. The average 

 student may not appreciate the book, as it is not 

 an "examination" manual. The time must soon 

 come when the present system of practical exam- 

 inations will be abandoned. Teachers should 

 certify that their students have done a well- 

 arranged course, and can do the experiments if 

 given the proper opportunities.* 



Students of chemistry and physics will also 

 find the book helpful in their work ; many obscure 

 points in their abstract information will be made 

 clear by the descriptions here given. We agree 

 with Prof. Bayliss that all beginners should have 

 a course of general physiology, and we would 

 fain see a return to the old system in which every 

 science student worked through a course in 

 physics, chemistry, and biology. The modern 

 student has too restricted an outlook on one side 

 or the other. 



NO. 2625, VOL. 104] 



UENDEUSM. 

 Mendelism. By Reginald Crundall Punnett. 

 Fifth edition. Pp. xv + 219 + vii plates. (Lon- 

 don : Macmillan and Co., Ltd., 1919.) Price 

 75. 6d. net. 



IN reviewing a new edition of a book so well 

 known as Prof. Punnett's "Mendelism," it is 

 unnecessary to notice more than the changes that 

 have been made as compared with previous 

 editions. The third edition (191 1) was, in fact, 

 a new book, and the fourth (1912) was substan- 

 tially similar, with a certain amount of revision. 

 Seven years have now passed, and although the 

 war seriously interfered with genetic research 

 in Europe, great progress in certain directions 

 has been made in America, and it is to incorporate 

 this new work that the chief changes in the present 

 edition have been made. The first eight chapters 

 are substantially unchanged, and comparatively 

 little alteration has been made in the chapters on 

 the economic aspect of genetics, on variation and 

 evolution, and on man. To the chapter on inter- 

 mediates there has been added an account of 

 Nilsson-Ehle's theory of multiple factors as illus- 

 trated by his work on colour factors in wheat, 

 by Davenport's work on mulattoes, and bv Prof. 

 Punnett's own work on the size-inheritance of 

 fowls. Some special cases, such as that of 

 doubleness in stocks, that were mentioned under 

 various headings in previous editions are col- 

 lected together into a special chapter on " Certain 

 Complications." We note with regret that the 

 hypothesis of "multiple allelomorphs," as illus- 

 trated by Nabours' experiments on grasshoppers 

 and by certain characters in Drosophila — a hypo- 

 thesis regarded by many as a preferable alterna- 

 tive to the presence-and-absence theory — is no- 

 where fully discussed. 



The remaining changes and additions are almost 

 entirely concerned directly or indirectly with the 

 work of Prof. T. H. Morgan and his school on 

 Drosophila — with the relations, that is to say, 

 between Mendelian characters and sex, and with 

 the theory that both Mendelian characters and 

 sex are transmitted by chromosomes. Of the 

 two chapters on sex, the first has been rearranged 

 with some additions, but the revision has resulted 

 (p. 92) in a reference to Abraxas as a case already 

 described, while in fact it is not mentioned until 

 p. 96. Incidentally, in this connection, it is an 

 error to say that var. lacticolor has been recorded 

 only in the south of Great Britain ; the stock 

 from which all or nearly all those now existing 

 were derived came from Lancashire. We regret, 

 also, that in this chapter the author has retained 



