628 Recently published Ornithological Works. 



possible for us to give a full analysis of it, but the summary 

 of results should certainly be carefully studied by all 

 interested in the subject, and compared with those of other 

 writers. We often have to draw attention to the full and 

 accurate work of our American cousins in articles of this 

 description, while here the details are illustrated by nine 

 excellent plates of sections of feather-germs and parts of the 

 feather. Mr. Strong does not consider that the question of 

 change of colour without moult can be properly studied apart 

 from a thorough consideration of the causes of colour and 

 its development, and he therefore conducts us afresh through 

 the details of both these processes, on the strength of material 

 obtained from specimens of Sterna hirundo, the Common 

 Dove, Megascops asio, and various Passeres, his conclusion 

 being li that there is no satisfactory evidence of a process of 

 rcpigmentation, and that the histological conditions of the 

 feather render such a process highly improbable." 



141. Strong on the Study of Variation. 



[A Quantitative Study of Variation in the smaller North-American 

 Shrikes. By R. M. Strong. American Nat. xxxv. pp. 271-298 (1901).] 



This elaborate article attempts to apply the " Precise 

 Criticism of Species" of Davenport ('Science/ n. s. vii. 

 p. 685) to Lanius ludovicianus and its races excubitoroides 

 and gambeli, 294 specimens of which were obtained for the 

 purpose from the United States, Mexico, and South Canada. 

 The characters taken into consideration, and for the most 

 part expressed in " frequency polygons," are : — Length of 

 wing, tail, and bill ; depth of bill ; colour of top of head, 

 upper tail-coverts, and breast ; while the curvature of the 

 bill is measured in 47 individuals by an ingenious method of 

 ascertaining the angle between certain chosen lines. 



The relative variability of the different characters in 

 different geographical areas is thus made evident ; and the 

 author asks us to consider whether it is worth while 

 encumbering nomenclature with the names of races based on 

 such slight variations, since the process of " splitting " could 

 be carried on ad infinitum by a well-trained eye. We are 



