88 Recent Lifcratiire. T^"** 



LJan. 



is the coloring- of various parts of a piece of agate} Likewise in the barb 

 and rhachis, pigment is definitely and permanently located either in tlie 

 solid cortex or in effectually separated cells of the medulla ; and there are 

 no pores large enough to admit the passage of melanin granules. The 

 characteristic longitudinal arrangement of melanin granules, which one 

 finds at the close of cornification of the feather, is permanent .... 



" When the feather is completed, the dermal pulp possesses no func- 

 tional connection with it ; the barbs and barbules are then practically 

 isolated from the vital processes of the organism and have no further 

 power of growth. 



" The arguments against change of color without molt through repig- 

 mentation or regeneration may be summed up as follows : 



" I. Most feather pigments are too resistant to chemical reagents to 

 w^irrant belief in their solution and ledistribution. 



" 2. Pigmentation of the feather has been observed to take place onlv 

 in the younger stages of the feather germ. 



" 3. At the end of cornification melanin granules have a definite 

 arrangement, which is permanent. 



" 4. When cornification has ensued, the various elements of the feather 

 are hard, more or less solid, structures and their pigment contents are 

 effectually isolated from one another. 



" 5. There is no satisfactory evidence of the occurrence of repigmen- 

 tation, and all the histological conditions render such an event highlv 

 improbable." 



The results of his histological studies on the formation and growth of 

 the feather, the differentiation of the various parts of its structure, the 

 origin and supply of pigment to the feather, etc., are summarized in six- 

 teen numbered pai-agraphs at the close of the paper, from which we quote 

 the following : 



" 15. Before cornification has ceased, all the pigment which the feather 

 is ever to receive has been supplied to the cells composing its fundament 

 [the growing base of the feather]. 



" 16. Changes in the color of plumage may take place (i) by a molt, 

 during which the new feathers may have the same pigmentation as their 

 predecessors or a different one ; (2) by a loss of certain portions of the 

 feather ; or (3) by physical disintegration in the cortex of the feather as 

 the result of exposure. There is no satisfactory evidence of a process of 

 repigmentation, and the histological conditions of the feather render such 

 a process highly improbable." 



Dr. Strong's paper is one of the most noteworthy ornithological papers 

 of the year, and should go far toward the settlement of the much dis- 

 cussed question of the repigmentation of feathers. We have here the 

 results of an impartial investigation by an expert histologist, in opposi- 

 tion to speculation and conjecture, put forth by persons untrained in 

 modern histological methods. — J. A. A. 



1 Not italicized in the original. 



