Febbuaet 12, 1909] 



SCIENCE 



261 



Principles of Breeding. A treatise on threm- 

 matology, or the principles and practises 

 inyolved in the economic improvement of 

 domesticated animals and plants. By E. 

 Davenport, M.Agr., LL.D., with appendix 

 by H. L. EiETZ, Ph.D. Boston, Ginn & Co. 

 1907. Pp. xiii + 727. 



It is likely that most writers will follow 

 Bateson in using the broader term " genetics " 

 for the subjects covered in this volume, rather 

 than the older and more restricted term 

 " thremmatology," proposed by Lankester, 

 even if for no other reason than ease of pro- 

 nunciation. However this may be, contem- 

 porary investigators seeking the facts of de- 

 velopment, variation and heredity are fast 

 accumulating vast quantities of data, past 

 investigations are receiving renewed atten- 

 tion in the light of recent discoveries, and the 

 author who undertakes the often thankless 

 task of compiling a text-book from the varied 

 lines upon which these subjects border, de- 

 serves the gratitude of all who are interested 

 in the field. Dr. Davenport brings to his aid 

 fifteen years' experience in presenting these 

 matters in the class-room, and the result is a 

 well-planned and logically developed treatise, 

 written in such clear English that a college 

 student should have little difficulty in seeing 

 the matter with the author's eyes. It may be 

 that all students of genetics will not accept 

 his views upon disputed subjects, for they are 

 the views of an ardent biometrieian ; it is 

 positive that there will be a difference of 

 opinion as to the relative importance of cer- 

 tain phases of the subject; yet this is the fate 

 of all text-books, particularly those in a new 

 field. There is hardly a doubt but that the 

 statistical method of dealing with problems of 

 heredity is unduly favored; and when the 

 author asserts that " it is the only reliable 

 method of attacking problems in transmis- 

 sion," cytologists and investigators using 

 pedigree culture methods will lend their ap- 

 probation only so far as to admit that a 

 knowledge of the theory of statistics is a 

 valuable adjunct to any line of work. On 

 the other hand, the method of handling the 



older debated questions of general biology — 

 •acquired characters, etc., — is eminently fair 

 and equitable. 



The book is divided into four parts: in the 

 first three, of increasing length, are discussed 

 the kinds of variation, the caiises of variation, 

 and the transmission of characters, wlile the 

 much shorter fourth part is devoted to practi- 

 cal problems. In a short appendix Dr. Rietz 

 gives an excellent introduction to the theory 

 of probabilities. Additional literature is 

 cited at the end of each chapter, which, in the 

 hands of a teacher familiar with all branches 

 of the subject, would be a valuable basis from 

 which to make selected lists for collateral 

 reading. Unfortunately the classics cited 

 are not distinguished from absolutely value- 

 less articles, and such extended lists might 

 thereby become rather more of a hindrance 

 than a help. The originals are cited only 

 when in English; the foreign work, which 

 forms a large portion of the literature in 

 genetics, is therefore noticed only in the form 

 of English abstracts. 



After an introductory chapter on the gen- 

 eral nature of variability, variation is treated 

 under the heads morphological, substantive, 

 meristie, functional and mutational. The 

 discussion under the first two heads, variations 

 in size and quality, are quite short. We miss 

 any consideration of the facts relating to the 

 difference between mere bigness due to nutri- 

 tion and inherited size due to gametic struc- 

 ture, which from its importance to the breeder 

 we might reasonably expect. More extended 

 treatment is given to the third type, the ex- 

 amples and text figures being drawn almost 

 wholly from Bateson. Under functional or 

 physiological variation, however, we are in- 

 debted to the author for a wealth of new illus- 

 trations, many of which are from experiments 

 with beef and dairy cattle and with maize, 

 that have never before been published. Under 

 mutations the author gives to the reader the 

 same impression (and the reviewer believes 

 this time unintentionally) that has caused, 

 and is still causing, false impressions among 

 out and out Darwinians as to the true con- 



