Reviews — Shan States, Burma. 127 



and Cope, early developed those methods of precise and detailed 

 observation of fact followed by critical analysis, which, favoured by 

 the discovery of abundant material, liave led to the refinement of 

 modern mammalian classification until it probably does represent with 

 great accuracy the real relations of the animals with which it deals. 



The expeditions of the American Museum, well directed and long- 

 continued, have brought togetlier so large an amount of accurately 

 horizoned material of Titanotheres that the evolution of that group 

 is known in very great detail ; in fact, to a large extent a phylogenetic 

 sclieme is a real genealogical tree, and not merely a short method of 

 indicating approximate relationships. Study of this unique material 

 has led Professor H. F. Osborn to many generalizations, which are 

 summed up in the works listed at the head of this review. The most 

 important of these are — (1) that definite characters, such as horns, 

 develop continuously by minute and almost imperceptible additions; 

 (2) that in separate branches of the same stock, horns arrive 

 independently on the same region of the skull. 



These conclusions are of great biological importance ; the ontogeny 

 of the horns of cattle is so exactly similar to the phylogeny of those 

 of Titanotheres as to render natural the conclusion that the horns of 

 cattle have originated in the same way by continuous variation. Yet 

 we know that liornedness is a mendelian allelomorph in cattle, so that 

 this conclusion of Osborn's to a great extent cuts the ground from 

 under the feet of de Vries and the ' mutationists '. 



Another line of pal aeon tological work which has been pursued with 

 very great success by Professor Osborn is the study of the wanderings 

 of mammals over the earth througli Tertiary time, a study which 

 depends for its success on detailed knowledge of the individual types 

 dealt with, and on the accuracy of our knowledge of their periods. 

 It may almost be said that this modern study is the invention of 

 Professor Osborn ; at any rate, he is its most successful exponent. 



II. — Shan States, Bukma. 



Geology of the Nokthekn Shan States. By T. H. D. La Touche. 



Mem. Geol. Surv. India, xxxix (2), 1913. pp. 380, xlii, with 



27 plates and 3 coloured maps at 4 miles to 1 inch. Price 



3 rupees or 4s. 

 MIHE present memoir must be considered, not as a complete 



JL account of the Northern Shan States, but merely as a pre- 

 liminary attempt to bring into order the observations made by my 

 colleagues and myself : to furnish a basis, which I can only trust may 

 be found to possess a certain degree of stability, on which future 

 geologists may work ; and to connect, as far as possible, the geology 

 of this interesting tract with that of the surrounding regions. The 

 area dealt with in these pages is almost twice the size of that of 

 Wales, and it contains a sequence of rocks that for variety and 

 complexity of structure may be compared with those that are found 

 in that country, but with very few facilities for observation. It is 

 covered for tlie most part with'forcst, or with grass so tall and dense 

 that it is often impossible to force one's way through it; traversed by 



