428 



SCIENCE. 



[N. S. Vol. XXIII. No. 585. 



ephemerceformis) weaves a band of silk 

 around the smaller twigs of many trees 

 about the beginning of September. The 

 cocoons remain on the trees over winter 

 and in the great majority of cases drop to 

 the ground in May or June of the following 

 year, because the bands which hold them 

 are torn as the twig increases in diameter. 

 Now and then, however, the bands are so 

 strong that they act as a ligature, causing 

 the swelling of the tissues on one or both 

 sides of the band. The swellings on the 

 upper and lower sides usually join after 

 several years, imbedding the band com- 

 pletely. Swellings were described and 

 shown on soft maple, sycamore, red gum, 

 oak, Virginia pine, sassafras, red cedar, 

 arbor-vitje, apple, robinia, deodar cedar, 

 willow, Cottonwood, cypress. 



Several hundred bands were broken to 

 test their strength, and the radial pressure 

 which they exerted on the twig was calcu- 

 lated. As most of the bands are broken by 

 the growth of the twigs every year, these 

 bands were taken as a measure of the en- 

 ergy exerted by the twig. The pressure 

 necessary to break them was determined to 

 be about 35-45 atmospheres per square 

 millimeter. Under pressures of 20-30 at- 

 mospheres the cambium still forms wood 

 cells, which differ from the normal wood in 

 having thicker walls, and a smaller lumen. 

 A smaller number of vessels are formed. 

 The results are considered as preliminary 

 and more extended data were promised. 



W. F. Ganong, 



Secretary. 



NOETHAMPTON, MaSS. 



SCIENTIFIC BOOKS. 

 Allgemeine Biologic. Zweite Auflage des 

 Lehrbuchs 'Die Zelle und die Gewebe.' 

 Von Oscar Hertwig. Pp. 649, mit 371 

 Abbildungen im Text. Jena, Gustav 

 Fischer. 1906. 

 This book is a second edition of ' Die Zelle 



und die Gewebe,' which originally appeared 

 in two parts, the first dealing with the general 

 morphology and physiology of the cell, in 

 1892, and the second dealing with the cell in 

 heredity and development, in 1898. Since 

 the publication of the first part fourteen years 

 have elapsed, and eight years since the pub- 

 lication of part two. These have been very 

 fruitful years in the history of the subjects 

 with which Professor Hertwig deals; concep- 

 tions of the morphology and physiology of 

 the cell, current at the time of the first edition, 

 have in some cases been greatly enlarged by 

 new discoveries, and in other cases entirely 

 superseded. Facts and ideas of prime impor- 

 tance concerning the chemistry of protoplasm, 

 the so-called tropisms, the phenomena of cell- 

 division, of maturation, fertilization, the 

 physiology of development and the origin of 

 species, have been set forth by numerous 

 writers. The value of the present book must, 

 therefore, be measured largely by the author's 

 assimilation of the new data and by their in- 

 corporation within his original system in a 

 logical manner, or else by logical development 

 of a new system rendered necessary by the 

 new data. 



Let us see to what extent the new edition 

 measures up to these requirements: (1) The 

 number of pages of the new edition is 649, 

 and of the two parts of the first edition 610; 

 the number of figures has been increased from 

 257 to 371. There has been, therefore, con- 

 siderable expansion; in many places new mat- 

 ter has replaced the old, entire sections have 

 been completely rewritten, new sections have 

 been added and there has been a certain 

 amount of rearrangement. The main addi- 

 tions are Chapter IV., dealing with the con- 

 ception of causation as applied to biology, 

 part of Chapter VIII., dealing with problems 

 of karyokinesis, and most of Chapter XI., 

 dealing with the maturation phenomena of 

 ova and spermatozoa. (2) On the other hand, 

 the author has not attempted to incorporate 

 any of the results of the chemistry of proteids 

 or of the applications of physical chemistry to 

 the study of protoplasm, although there is a 

 chapter on the chemistry of the cell; he has 

 not availed himself of any of the literature 



