MaV 2 1, 1908] 



NATURE 



51 



only discrepancy in this interpretation is the fact that 

 Carus recorded Cynthia rustica (=5. grossularia) as 

 well as T. sylvani from the Scilly Islands. Presum- 

 ably the former term was restricted to the less 

 crowded clusters in which the larvae had not fixed 

 themselves to the bodies of their parents. 



W'ALTER G.\RSTAXG. 



PRINCIPLES OF BREEDING. 

 Principles of Breeding. A Treatise on Thremmat- 

 ology. By E. Davenport, with appendix by H. L. 

 Rietz. Pp. xiii+727. Country I^ife Education 

 Series. (Boston, New York, Chicago, London : 

 Ginn and Company, n.d.) Price I2i, bd. 



THI.S is the first serious attempt to present a 

 modern scientific text-book on the principles of 

 breeding (or, as the author prefers to call it, threm- 

 matologv) to English-speaking agricultural students, 

 in which recognition is accorded to much of the recent 

 work done on genetics and some other branches of 

 the physiology of the generative system, and in which 

 effort is made to show the essential value of that 

 work to breeders. The book is most welcome, and 

 our thanks are due for it to the professor of threm- 

 matology in the University of Illinois. 



The author's idea of what is needful for tlie educa- 

 tion of an agricultural student is very far in advance 

 of what is usually considered sufficient for that pur- 

 pose; his book is adapted not only to convev a much 

 wider knowledge of scientific work than has been 

 hitherto thought necessary, but to demonstrate the 

 direct effect such work must have on the fortunes, the 

 ultimate success, of the modern practical breeder. 



In spite of the fact that Prof. Davenport declares 

 the breeder of the future will be a book-keeper and 

 statistician, his book shows he has a somewhat wider 

 appreciation of the breeder's qualifications than these 

 words indicate. At the same time, it does seem 

 possible that his enthusiasm for the pure science of 

 genetics has led him to load his book somewhat too 

 heavily with figures, and to neglect to inculcate with 

 sufficient force the necessity for a breeder's close 

 attention to and intimate knowledge of the capacities 

 and peculiarities of individual members of a flock or 

 herd. This is, in our opinion, a serious defect in a 

 text-book for agricultural students ; the power of close 

 observation is an essential qualification for a breeder. 



Similarly, the author's endeavour to induce the 

 student to take " short cuts " to success is to be depre- 

 cated. He urges " A man must realise the fruit of his 

 own labours." " The breeder must therefore work 

 faster than nature." The "evolutionary principle" 

 must be accelerated; and so forth. In so far as it is 

 possible to gain these ends his attempts to further 

 them are good, but he omits to point out that at the 

 best these ends can be only partiallv gained, and 

 that the evolutionary principle cannot be accelerated 

 sufficiently to satisfy individual aims. He notes that 

 '■ experience shows that the purposes, standards, and 

 methods of a successful breeder are seldom handed 

 down from one man to another," but he does not 

 atteinpt to point out the means whereby this can be 

 NO. 2012. VOL. Soi, 



obviated, and yet it is the most severe handicap to 

 progress which breeders suffer from. 



There is one great opportunity which all professors 

 of a big agricultural college have to their hand, that 

 of organising a system of records of the practical 

 results subsequently gained by all the students which 

 pass through their schools. Such records, compiled 

 by men trained by modern scientific methods and 

 made available for use at their college, would be of 

 incalculable value, both to the professors and the 

 breeders of future generations ; in order to carry out 

 such a scheme, however, the student must be taught 

 to understand that there are no short cuts to know- 

 ledge, and that the only way they can hope 10 

 accelerate the acquisition of knowledge of evolutionary 

 principles is by pooling their e.xperiences, their 

 failures as well as their successes. 



Part i., on variation — the author makes variation 

 rather than heredity the initial leading thought of his 

 scheme, putting the cart before the horse and thereby 

 somewhat confusing the issue — is a brief risumi of 

 some of the leading features of that branch of the 

 subject, instances being given of a kind specially suit- 

 able to stimulate the interest of American students, for 

 whom the book is written. 



Part ii., on the causes of variation and the relative 

 stability of living matter, and part iii., on trans- 

 mission, constitute the bulk of the book. The author's 

 clear and forcible writing, the thoroughness of his 

 treatment, the arrangement of his facts, and the 

 wealth of illustration he gives are worthy of great 

 praise. These sections are not only a valuable sum- 

 marv of what is known, but contain much original 

 thought, and deserve the attention of all students of 

 the subject. 



Part iv. is on practical problems. Those dealt 

 with under the headings selection, systems of breed- 

 ing, plant breeding, and animal breeding are full of 

 good common sense and sound advice ; any breeder 

 would do well to consult them. 



Thus if it has failings the book has great merit, 

 and it is to be hoped the example set by Prof. Daven- 

 port will be followed in this country, where the educa- 

 tion of agricultural students in the science of breeding 

 is sadiv behindhand. 



THERMOCHEMISTR Y. 

 TSiermnchemistry. By Julius Thomsen ; translated 

 from the Danish by Katharine A. Burke. Pp. 

 xv-t-495. (London: Longmans, Green .ind Co., 

 U|oS.) Price 95. 



OWING to the rapid strides which have recently 

 been made in physical chemistry, the subject of 

 thermochemistry, which is itself of a physical nature, 

 has been rather left in the background. At one time 

 it was hoped that thermochemistry would be of very 

 great help in elucidating the hidden laws governing 

 chemical reactions, but unfortunately it has hardly 

 realised expectations. 



.Mthough a very large amount of work has been done 

 upon this subject, we can hardly say that it has been 

 found possible to rely upon thermochemical methods 



