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THE AMERICAN NATURALIST 



[Vol. LII 



mutations comprise the remainder of part one. The discussion 

 of mutations will probably not please DeVries, but it certainly 

 is more in accord with all the facts than most other essays on 

 the subject. 



The applied genetics, animal breeding and plant breeding, 

 filling twenty-four chapters, ought to be received with great 

 approbation. Its compilation must have been very difficult, 

 and its usefulness should be in direct proportion to the work 

 involved. There is a great deal of new material of a strictly 

 practical nature such as the origin of sweet pea varieties, breed- 

 ing disease-resistant plants, etc. On the other hand, there is 

 really no definite line to be drawn between part one and parts 

 two and three. Theoretical genetics runs all through the book. 

 For example one finds the treatment of heterosis, graft-hybrid 

 chimeras and bud mutations in part two; and in part three dis- 

 cussions of Mendelian inheritance in domestic animals, acquired 

 characters, non-Mendelian theories of sex-determination, the hor- 

 mone theory, etc. The work is so well done that it must be read 

 to be appreciated. The reviewer has but one suggestion to make 

 concerning it, and this not in the nature of a criticism. Par- 

 tially sterile hybrids between species, as is shown in Chapter 12, 

 supply particularly useful material for the improvement of do- 

 mestic animals and cultivated plants. If one studies carefully 

 the history of domestic species, fragmentary as it is, he is as- 

 tounded at the enormous number of eases in which the ancestry 

 involves two or more species. Would it not be well to empha- 

 size this point by extended illustrations in a book on plant and 

 animal breeding? 



The authors are to be congratulated on having brought to- 

 gether the material for a classical text-book on genetics. Re- 

 vision will doubtless soon be necessary as is suggested in the 

 preface. If it is made with the care that such an excellent 

 foundation deserves the work will unquestionably go through 

 many editions. 



The McGraw-Hill Company deserve no little credit for the 

 generous way in which they have seconded the authors' efforts. 

 The typography, illustrations, paper and binding are extremely 

 good. We understand that this is their first contribution toward 

 a series of agricultural <±ext-books under the general editorship 

 of C. V. Piper. A standard has been set that is a good augury 

 for the future. 



