June 26, 1919] 



NATURE 



323 



Those who have followed his researches, no less 

 than those who are not acquainted with the 

 illuminating- results of his work, will heartily 

 welcome this small volume (one of a new American 

 series, inspired, as the editors tell us, by the series 

 of British monographs on physiology- and bio- 

 chemistry), in which he has collected his scattered 

 papers and woven their contents into a clearly 

 co-ordinated and simple story. 



The book deals mainly with the neuro-muscular 

 system of "the three simpler phyla of the multi- 

 cellular animals, the spong-es, the coelenterates, 

 and the ctenophores, " but some of the most 

 illuminating passages in the work deal with the 

 survival of such primitive mechanisms in the heart, 

 the alimentary canal, and other parts of the 

 higher vertebrates. This much-tilled field of 

 research was well worth re-cultivating; and 

 Prof. Parker has been able to clear away much of 

 the uncertainty and confusion in the results 

 obtained by earlier workers, and to bring- to light 

 many new points that had escaped notice before. 



Although it must be obvious that the functions 

 of the most primitive nervous system, as an 

 instrument to quicken and direct the response to 

 changes in the animal's environment, pre- 

 suppose the existence of a muscular system to 

 perform such quick and precise actions, it 

 remained for Prof. Parker to discover that the 

 differentiation of muscle did actually precede the 

 appearance of a nervous system. 



Another important feature of the book is the 

 convincing series of ingenious experiments to clear 

 up the difficulties of the problem of nervous trans- 

 mission in sea-anemones. 



Prof. Parker seems to adopt the tradition 

 of the text-books of physiology for students that 

 the most primitive type of nervous system is of 

 the two-celled receptor-effector type — simply a 

 specialised sensory cell put into connection with 

 a neighbouring muscle either directly or through 

 the intermediation of a nerve-cell. But it is 

 difficult to conceive of the biological usefulness 

 of such an arrangement of isolated neuro-muscular 

 units ; and, so far as I am aware, there is no 

 evidence of its existence, except in conjunction 

 with a system that links up the whole organism. 

 As Prof. Parker himself has shown (pp. 94 and 

 95), stimulation of one spot (in an animal pro- 

 vided with the most primitive type of nervous 

 system) excites a response of the whole animal, 

 and not merely of a single muscle-fibre. 



G. Elliot Smith. 



OVR BOOKSHELF. 



A Practical Handbook of British Birds. Edited 



by H. F. Witherby. Part i. Pp. xvi-f64. 



(London: Witherby and Co., 1919.) Price 45. 



net. 



Ornithologv, judged by its voluminous and 



ever-increasing literature, is to be regarded 



as one of the most attractive branches of 



natural science studied in the British Isles, and 



the works devoted to our native birds are amongst I 



NO. 2591, VOL. 103] 



the most popular of all. The appearance of yet 

 another book on British birds may be welcomed, 

 since it brings our knowledge of the subject up 

 to date. In recent years great changes have been 

 made in the scientific nomenclature of ornithology, 

 and, alas ! are still in progress, while the recog- 

 nition of numerous racial forms among the birds 

 on the British list has rendered the study of the 

 varied members of our avifauna difficult, especially 

 for the field observer, and hence has given a great 

 impetus to collecting. In addition to these major 

 changes, important advances have been made in 

 our knowledge of the many and complicated 

 movements of migratory birds witnessed on our 

 shores ; and also the periods of moulting and 

 other changes in plumage. All these come within 

 the scope of the work under consideration. 



The information under each species is divided 

 into sections, and dealt with throughout in uni- 

 form order. These sections include keys to the 

 various groups from orders to species, plumages, 

 nesting, food, distribution, etc. While this 

 method of treatment has its advantages in brevity, 

 it detracts much from the literary aspect of the 

 work, and renders it unattractive reading. 

 Though the plan has been carefully carried out, 

 the sections lack uniformity in treatment, inas- 

 much as those devoted to plumages are redun- 

 dant as compared with the rest. The shorter the 

 accounts of plumages the better, provided they 

 are adequate, for unnecessary details are neither 

 conducive to lucidity nor helpful. As regards the 

 illustrations, the coloured pjates (of which there 

 are to be twelve) are good, and the text figures 

 (which are numerous), though satisfactory on the 

 whole, are in many cases poor,, and in others un- 

 necessary. It is a sign of the times that. a hand- 

 book on British birds, professedly compact and 

 concise, should run to 1200 pages. The work is 

 to be issued at intervals in eighteen parts, and 

 when complete will form two volumes. 



Soils and Fertilisers. By Prof. T* L. Lyon. 



Pp. xxii + 255. (New York: The Macmillan 



Co.; London: Macmillan and Co., Ltd., 1918.) 



Price 65. 6d. net. ' 

 This little book is written chiefly for elementary 

 students in secondary agricultural schools, for 

 short-course students in colleges, and for teachers 

 attending summer courses. A good deal of the 

 material is drawn from the author's well-known 

 larger work on soils, which was written for 

 senior students. In spite of differences of con- 

 dkions here and in the United States, the English 

 teacher will find the book of interest as being a 

 compact summary of the points which an Ameri- 

 can teacher brings before his students. 



The first three chapters deal with soil forma- 

 tion, a subject which in this country is left to the 

 geologist, the soil student taking the soil as he 

 finds it and not concerning himself with its origin. 

 Then follows a section on soil water, which in 

 many parts of the States is of great practical 

 importance, and in any case presents mari> 

 features of scientific and educational interest. 



