582 EMBEYOLOGY OF THE LOWEE VEETEBEATES app. 



photographically and inserted in the text hi contiguity with the passage 

 which they illustrate. Their function is to render more clear the 

 statements of the author : they represent as accurately as possible 

 phenomena as observed by the skilled and trained eye with a brain 

 behind it. Actual photographs, which represent merely details lying in 

 one particular plane and as seen by the untrained photographic lens, 

 should be avoided. Apart from the imperfections indicated they are so 

 blurred by the ordinary processes of reproduction as to be liable to 

 misinterpretation and in these days of skilful manipulation they are of 

 course useless as guarantees of truth. 



