234 



NATURE 



L August 25, 19 10 



diagnosis and nomenclature. For instance, the true 

 relationship of the Rhizoctonia fungus which causes 

 diseases of various cultivated plants is made clear ; 

 the Rhizoctonia disease of potatoes is the same in 

 Europe and America, while R. medicagiiiis, which 

 attacks lucerne, asparagus, and sugar-beet in Europe, 

 is a distinct species which does not occur in America. 



Since many of the fungus diseases described occur 

 in England, there is a considerable amount of in- 

 formation of direct practical value to the fruit-grower 

 and market-gardener in this country. We find, for 

 instance, an account of the recently discovered bud 

 infection of peaches in the case of the peach "leaf- 

 curl " fungus {Exoasciis deformans), and of the best 

 method of treating this disease. Excellent descrip- 

 tions are given of such common diseases as the 

 "brown rot" of fruit-trees (Sclerotima fructigciia) 

 and apple and pear "scab" (Ventiiria pomi and T'. 

 firina). Especially interesting is the account given of 

 the various apple " cankers " which occur in the 

 United States — the "blight canker" (Bacillus 

 amylovonis), the "blister canker" (Niimmiilaria dis- 

 crcta). the "European apple canker" (Nectria Jitis- 

 sima), the "bitter-rot canker" (Glomerclla riifo-macu- 

 lans), and the " Liack-rot canker" (Sphaeropsis 

 lualorum). A sharp look-out for the American 

 " canker "-producing fungi should be kept bv the 

 apple-grower and economic mycologist in this country. 

 It may be noted here that the Sphaeropsis-canker has 

 just been detected in Surrey. The exact appearance 

 of the injury produced on the bark by the various 

 "canker" fungi is shown by means of excellently 

 reproduced photographs ; one is tempted to say that 

 Prof. U'hetzel's photograph at Fig. 170 of the 

 " Sph»ropsis-canker " is the best of its class that has 

 appeared in any book. 



One of the most interesting chapters deals with 

 the recent outbreak in the States of the European 

 currant rust (Cronartium ribicola), a disease which 

 -was unknown in .Vmerica until 1906. Investigation 

 ■showed that the fungus was being introduced in its 

 necidial stage on seedlings of white pine (Pinus 

 strobiis) imported from Germany. A determined 

 ■effort is being made to destroy all the diseased pines 

 which have been introduced, and to prevent further 

 importation of infected seedlings. 



Sufificient has been said as to the scope of this work 

 to indicate that it can be heartily recommended to 

 the student of fungus diseases in this country; it 

 is, in fact, indispensable, for no such manual pre- 

 viously existed in this country. E. S. Salmon. 



HERT WIG'S TREATISE ON ZOOLOGY. 

 Lehrbuch der Zoologie. By Prof. R. Hertwig. Pp. 

 xii + 670. Neunte Auflage. (Jena: G. Fischer, 1910.) 

 Price 11.50 marks. 



THE new editions of Prof. Hertwig's text-book of 

 zoology follow one another with such startling 

 rapidity that it must be clear to everyone that on the 

 continent at least it must have met with extraordinary 

 success. This is perhaps not surprising, for, apart 

 from the influence which Prof. Richard Hertwig's 

 NO. 2130, VOL. 84] 



prominent position aniong the zoologists of the world 

 niu-,t command, the "Lehrbuch der Zoologie" is cer^ 

 t.-iinlv one of the best — if not the best — treatises on the 

 subject in the German language. 



There was a time not so very long ago when the 

 English student of zoology was almost dependent upon 

 the translations of the text-books of German authors, 

 but in later years his wants have been supplied by 

 his own countrymen, and it does not seem probable 

 thai Prof. Hertwig's book, excellent as it is in many 

 respects, will find a large circulation in this country. 



If it should fall into the hands of our own students, 

 the parts which thev will find most useful are those 

 which deal with the more general problems of cytology, 

 fertilisation, and inheritance. On these subjects the 

 author writes with the authority of one whose own 

 personal researches and those of a large number of 

 his pupils have commanded the attention of the scien- 

 tific world, and although there may be many who 

 cannot fully accept the views set forth in explanation 

 of the facts, the charm of their concise statement and 

 the ingenious manner in which thev are woven to- 

 gether are bound to create interest and reflection. 



In dealing with the probleni of fertilisation, for 

 example. Prof. Hertwig considfrs that we can no'sv 

 accept — " mit grosses Bestimmtheit " — that it is the 

 chroniatic nuclear substance from which the chromo- 

 somes are derived that bear the hereditary characters, 

 and in support of this he quotes some striking' evidence 

 drawn from the recent researches on the cytology of 

 the germ-cells, and brings them into line with the 

 results of the Mendelian experiments on inheritance. 

 As Prof. Hertwig puts it, the theory seems very con- 

 vincing, but there are some authorities who still doubt 

 whether this theory will really bear the weight that 

 is put upon it, and we should like to see the evidence 

 that clearly tends to disprove it given some credit in 

 a book that should be an impartial review of the pre- 

 sent state of knowledge. 



In the systematic part of the book the student will 

 find a clear description of the principal characters of the 

 classes and orders of the animal kingdom illustrated 

 by many excellent figures. It cannot be expected that 

 in the attempt to cover such a wide field within the 

 limits of a single volume, the book will be entirely 

 free from serious omissions and inequalities of treat- 

 ment, but there are some features carried over from 

 the earlier editions which really require some amend- 

 ment if it is to maintain the undoubted success it has 

 already achieved. The Enteropneusta, for example, 

 are still classified as a class of worms. This is a posi- 

 tion which has still some defenders, and in itself does 

 not call for special comment ; but as the author 

 directs attention to the points of relationship between 

 Balanoglossus, Rhabdopleura, and Cephalodiscus, 

 surelv the student will expect to find some position 

 assigned in the text to the last two genera. 



There are several other points, too, in which the 

 bonk will hardly meet with the requirements of 

 modern students. There is no figure, and a very 

 meagre description of such important forms as 

 Kcenenia ;ind Anaspides ; there is no mention made of 

 the interesting trematode Temnocephalus. and, what 



