NATURE 



215 



THURSDAY, OCTOBER 24, 1912. 



THE DAWN OF LAND VERTEBRATES. 

 'American Permian Vertebrates. By Prof. S. \\'. 

 Williston. Pp. v+ 145 + 38 plates. (Chicag-o, 

 III. : The University of Chicago Press ; Cam- 

 bridge [Eng.] : University Press, n.d.) Price 

 los. net. 



IT is now evident that not only amphibians, but 

 also reptiles with considerable diversity of 

 habits and structure, arose in several parts of 

 the world before the close of the Carboniferous 

 period. It is thus becoming more and more diffi- 

 cult to interpret the relationships of the numerous 

 genera — even those known by complete skeletons 

 —which have already been described from the 

 Permian rocks of Europe, North America, Brazil, 

 and South Africa. 



Some years ago, when only a few types were 

 known, the direct passage from amphibians to 

 reptiles, and that from these early groups to 

 mammals, seemed to be almost discovered; but 

 later researches have complicated rather than 

 simplified the problem, and at present no satis- 

 factory classification is possible. Realising this 

 position. Prof. Williston and his colleagues are 

 devoting themselves to a precise description of 

 the numerous important skeletons and skeletal 

 fragments which they have obtained from the 

 Permian of Texas and New Mexico, and the 

 small, well-illustrated volume now before us is 

 one of the results. As Prof. Williston truly 

 remarks, "the chief need in the palaeontology of 

 the early vertebrates is more facts," and students 

 will gratefully accept the rich collection offered to 

 them in his new work. 



Photographs of restored skeletons of the 

 "heromorph reptiles Varanosaurus and Casea are 

 riven to show how astonishingly similar is their 

 general aspect to that of the contemporaneous 

 imphibian Eryops. Other figures and descrip- 

 tions suffice to indicate that there is no longer \ 

 any single skeletal character by which an early I 

 reptile can be distinguished' from an early [ 

 amphibian; but Prof. Williston thinks that when I 

 the sum-total of characters of a skeleton is con- j 

 sidered, there is still no difficulty in assigning the | 

 specimen to its true place in one or other of the 

 two classes. j 



In some groups the various modifications of the I 

 skull seem likely to prove as numerous as those ! 

 observable among modern lizards, so that caution ' 

 is necessary in dealing with fragments. These j 

 and other difficulties, however, can only be recog- 

 NO. 2243, VOL. gol 



nised and overcome through the progress of such 

 technical and detailed descriptive work as that 

 which we welcome from the professor of palaeon- 

 tology in the University of Chicago. 



A. S. W. 



SCIENCE OF THE SOIL. 

 Soil Conditions and Plant Gro-wth. By Dr. 

 Edward J. Russell. Pp. viii+168; with 

 diagrams. (London : Longmans, Green and 

 Co., 1912.) Price 55. net. 



HOW the chemist can help the farmer. He 

 can analyse the soil and the crop, and 

 by comparing the results of his analyses, can tell 

 the farmer how to manure his land so as to grow 

 profitable crops." The above is a quotation, as 

 nearly as the writer can remember, which formed 

 the preface to a syllabus on which he was asked 

 to give a course of local lectures about 

 twenty years ago, when local lectures were in full 

 swing under the newly-constituted technical educa- 

 tion committees of the county councils. 



At that time there was some excuse for such 

 misconceptions, for the literature of the some- 

 what hybrid subject known as agricultural 

 chemistry was scattered through numerous 

 periodicals, mostly in foreign languages, and by 

 no means easily accessible to the budding lec- 

 turer. Since then many excellent text-books have 

 been written, and are now in the hands of both 

 teachers and students. None of them, however, go 

 to the root of the matter, and give the substance 

 of the classical researches which should form the 

 foundations of the faith of the agricultural 

 chemist, as does Dr. Russell's excellent mono- 

 graph. 



Dr. Russell has made a comprehensive survey 

 of the literature of the subject so far as it deals 

 with the relations between the soil and the plant. 

 He has succeeded in giving the gist of the more 

 important and fundamental contributions to the 

 knowledge of the subject, and in pointing out 

 with true critical spirit what is really proved to 

 demonstration and in what directions further 

 investigation is necessary. 



His book will be of the greatest use both to the 

 teacher of agricultural chemistry and to the in- 

 vestigator — to the latter especially, as it will put 

 him in touch with the literature of the subject. It 

 can scarcely fail to stimulate in this country the 

 output of definite experimental work on the 

 various problems connected with plant-growth. 

 The chapter on soil analysis and its interpretation 

 will be particularly welcome to the staffs of the 

 several colleges who are engaged on soil surveys 



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