3 JULY 1926, Page 28

THE ORIGIN OF BIRDS. By Gerhard Hellmann. (H. F. and

0. Witherby. 20s. net.) Tins is a most valuable and interesting monograph, illus- trated by a hundred and forty photographs and drawings, and two plates in colour. The substance is severely technical and osteological researches may be seen to be particularly dry ; but Mr. Hellmann has attempted to make the book interesting to the ordinary educated man. He writes pic- torially where he can, and always makes his argument coherent. The tracing of the changes by which birds were evolved from reptiles includes most of our modern scientific knowledge, and we hope that this book will become, in its own way, something of a classic.