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THE AMERICAN NATURALIST [Vol. XLV 



work have been reviewed elsewhere (Cockerell, 1907), 

 but, in so far as I can find, the chemical data and theo- 

 rizing have been passed over. It is evident from a very 

 casual glance at the chemistry, that Tower has strayed 

 from familiar paths and is wandering far afield. I can 

 refer to only a few of his errors here, but these are so 

 obvious as to show that no reliance can be placed upon 

 the chemical findings, much less upon his chemical theo- 

 rizings. 



Perhaps the worst error, inasmuch as Tower bases all 

 of his results as to the nature of the pigment upon this 

 point, is to state (1906, p. 136), "Bottler, working upon 

 the hair of animals and upon silk, has shown these pig- 

 ments to be azo compounds, and in insects they belong 

 to the same series." The reference which Tower quotes 

 is a book by Bottler (1902) entitled 11 Die animalischen 

 Faserstoffe. Bin Hifls- unci Handbuch fiir die Praxis, 

 umfassend Vorkommen, Gewinnung, Eigenschaften und 

 technische Verwendung some Bleichen und Fdrben 

 thierischer Faserstoffe. Naeh dent gegenwiirtigen 

 Standpunkte der wissenschaft bearbeitet." From the 

 title I did not expect to find much original work on the 

 subject of annual pigments, neither could I find in any 

 of the biochemical literature any reference which could 

 be so construed as to intimate that animal fibers, espe- 

 cially silk, occurred naturally dyed with azo dyes. I 

 find in Bottler's book references to azo compounds in the 

 chapter on "Das Farben animalischer Faserstoffe" 

 and in each instance the references are to azo dyes with 

 which to dye the animal fibers. In almost every instance 

 Bottler gives the origin of the dye employed, as "M. L. 

 Br." {Meister, Lucius and Bruning) or (( Fr. Bay." (Fr. 

 Bayer & Co., in Elberfeld) together with explicit direc- 

 tions as to the composition of the dyeing bath. Bottler 

 does mention the naturally occurring pigments by stating 

 on page 36 that "dark-colored wools are usually used in 

 their natural color or dyed dark, as it is only with great 



