REVIEWS 355 



present time by the wastage of fine lives in the war. It is therefore desirable 

 that every student of biology, and every layman too for that matter, should be 

 informed in such matters. This information is made available in a readable 

 manner in the present volume, and although the author puts forward his own 

 views, this is done without prejudice to other schools of thought. The whole 

 forms a very fair and reasonable review of our knowledge in these two fascinating 

 fields of biological inquiry. C. H. O'D. 



The Fundus Ocnli of Birds especially as Viewed by the Ophthalmoscope. 



By Casey Albert Wood, M.D. [Pp. 180, with 145 drawings in the text 

 and 61 coloured paintings by A. W. Head, F.Z.S.] (Chicago: The 

 Lakeside Press, 191 7.) 

 The ophthalmoscopic examination of the eye of birds is a subject that has 

 received practically no attention from naturalist or ophthalmologist, and the 

 present volume lays a very satisfactory foundation for the bridging of the gap in 

 our knowledge. Wood, a well-known ophthalmologist, has been fortunate enough 

 to secure the co-operation of A. W. Head, whose skill in depicting the Fundus 

 oculi is well known, and the result is a beautifully illustrated volume. The 

 general "get-up" of the book is in keeping with the illustrations and is very 

 satisfactory. In probably no vertebrate group is so much variation met with in 

 this part of the eye as in birds, and the thorough examination of a large number 

 of different species suggests the possibility of utilising the conformation of the 

 fundus for systematic purposes. 



To one used to the fairly constant relation of the macula lutea with its fovea 

 in the mammals it comes as a surprise to find that oval, ovoid, circular, or quite 

 long ribbon-like areas of acute vision are found in birds. These also may be 

 supplied with two maculae fairly widely separated from one another, as, for 

 example, in the Flamingo (Phcenicopterus roseus). The great variation in the size, 

 shape, and complication of the pecten is also fully dealt with ; but although 

 several theories regarding its function have been advanced, it cannot yet be said 

 that any one of them is completely satisfactory, although it appears to be cor- 

 related with the relation between monocular and binocular vision. 



The fundi of certain other vertebrates have also been examined, and the 

 author says : " If one may draw any conclusion from such sparse material and 

 from such an incidental examination of the subject, it is that whatever of common 

 origin the avian and reptilian classes may have originally had the ornithological 

 branch left the parent stem with a subdivision of the Lacertilia and not with the 

 Ophidia." 



A useful Bibliography and account of the technique of ophthalmological 

 investigation is given, and it is interesting to note that the ordinary mydriatics 

 for dilatation of the pupil have little effect in birds, where, owing to the anatomical 

 relations of the lachrymal apparatus, drops instilled into the eye run down into 

 the oesophagus. The most successful agent in widening the pupils is a 1 per cent, 

 solution of nicotin, and the author suggests that the action is a general systemic 

 one and not specific for eye muscles alone. C. H. O'D. 



Three Lectures 011 Experimental Embryology. By J. W. Jenkinson, 



M.A., D.Sc. [Pp. xvi + 130, with 20 figures.] (Oxford : at the Clarendon 



Press, 1917. Price js. 6d. net.) 



Some of us have a vivid recollection of the delivery of these lectures a few years 



ago at University College, London, where Jenkinson practically laid the foundation 



