332 



DISCOVERY 



animal populations in the same way. In any country, 

 and on the ^iverage, the larger families and genera, 

 Dr. Willis, says, will be the older, and will occupy the 

 larger territory. To the idea of Age and Area he adds 

 that pf Size and Space. If groups of allied genera 

 be dealt with, the size of a genus (i.e. the number of 

 species it includes) is found to depend largely upon the 

 area it covers, that is, " ultimately upon its age." The 

 author's position is that natural selection no longer 

 concerns us ; there is a mechanical explanation of the 

 facts of distribution. Age supplies a measure of distri- 

 bution. The uniformity of the curves must be explained ; 

 there is clearly something underlying it. The question 

 is, has Dr. Willis found the correct explanation ? 



He has WTitten a stimulating book ; it is not all easy 

 reading, and one feels a suspicion that the author, carried 

 away by his enthusiasm, did not allow himself enough 

 time for critical revision of the manuscript. He has 

 stated his case ; and it is for those who disagree with the 

 conclusions to state theirs. That Dr. Willis has rendered 

 a valuable service to biological science the great majority 

 of his readers will concede ; he has directed attention 

 to a subject which has suffered neglect, and in support 

 of his thesis he has marshalled an imposing array of 

 facts. The Age and Area hypothesis is simple ; but 

 I venture to think that it does not furnish a solution of 

 the problem of geographical distribution considered in 

 its broader aspects. 



A. C. Seward. 



Elements of Plant Biology. By A. G. Tanslev, M.A., 

 F.R.S. (George Allen & Unwin, Ltd., 105.) 



" This book is intended," the author states in the 

 Preface, " primarily for medical students and others 

 who do not necessarily intend to continue the study of 

 Botany, but who desire or are obliged to obtain some 

 elementary knowledge of plants, particularly in relation 

 to general biology." In a recent number of Discovery, 

 a book by Professor Dixon, on lines very similar to 

 those followed by Mr. Tansley, was briefly reviewed. 

 The two books have much in common ; both are primarily 

 intended for medical students ; both break away from 

 the more formal method, that used to be in fashion, 

 of studying types rather from the morphological (that is, 

 the aspect of biology concerned with form and structure) 

 than from the physiological point of view ; and both 

 include admirable ■ guides to practical work. 



Mr. Tansley begins with a scholarly treatment of certain 

 subjects of fundamental biological importance : the 

 differences between plants and animals, organic substances 

 and their chemical characters, some physical characters 

 of organic substances, protoplasm and the Amcvba, the 

 vital functions, the cell. The suggestion may be offered 

 that these more difficult subjects would come better 

 after some account had been given of a typical green 

 plant. It is easier to interest the beginner in the materials 

 of which a plant is built after he has been introduced 

 to the main features of a plant as a living organism — 



a complex and efficient machine — than to begin by 

 descriptions of the nature of the materials of which 

 organisms are constructed. 



The main divisions of the plant-kingdom are then 

 passed in review and illustrated by good descrip- 

 tions of well-chosen examples : the lower plants are 

 dealt with first, an order that is both logical and most 

 likely to awaken the interest of students. Throughout 

 the book the wider aspects of biology are kept in view, 

 and frequent and apposite comparisons are made between 

 plants and animals, both from the standpoint of construc- 

 tion in relation to manner of life and from the point of 

 view of nutrition. Stress is laid upon subjects which 

 may reasonably be regarded as essential parts of the 

 equipment of a medical student, subjects which, indeed, 

 should be included in any scheme of liberal education. 



The book is clearly written and adequately illustrated : 

 the presentation of the subject is characterised by 

 accuracy and a philosophical outlook. It is probable 

 that some beginners will find certain parts rather difficult, 

 especially the chapter on " Some Physical Characters of 

 Organic Substances " ; but this surmise may be, and 

 probably is, largely due to the fact that many of the 

 older botanists — among which the reviewer includes 

 himself — received their training in the days when text- 

 books of botany did not deal with such subjects as 

 surface tension, surface energy, adsorption, colloids, and 

 other phenomena, the importance of which in biology 

 has only been recognised in comparatively recent times. 

 The most difficult art is to know what to emit ; it is 

 arguable that certain plants excluded by the author 

 might, with advantage, have been included in place of 

 some of those selected for treatment ; but whether or 

 not Mr. Tansley has made the best choice, the important 

 point is that he has produced an admirable te.xtbook. 

 which may be strongly recommended not only to students 

 in the narrower sense, but to all who wish to learn some- 

 thing of the mysteries of life and of the nature of the 

 problems suggested by the word " evolution." One is 

 sometimes asked to believe that it is superfluous for 

 medical students to be expected to acquire a knowledge 

 of botany. By his treatment of plant biology Mr. Tansley 

 has supplied a very powerful argument in favour of the 

 retention of botany in the medical curriculum, and has 

 demonstrated the possibility of treating the subject on 

 broad lines and making clear to any intelligent reader 

 the position of plants in the general scheme of living 

 beings. 



A. C. S. 



Secret Sects of Syria and the Lebanon. A Consideration 

 of their Origin, Creeds, and Religious Ceremonies, and 

 their Connection with and Influence upon Modern 

 Freemasonry. By Bernard H. Springett. (George 

 Allen & Unwin, Ltd.. 12.5. bd.) 



Several attempts have been made to connect the 

 Masonic order with the mystic religions of the East ; 

 but they have not commended themselves to the majority 

 of members of the Craft. Dr. Churchward, in his Arcana 



