GENESIS OF FAULT-BARS IN FEATHERS. 359 



Zenneck l has shown that in the case of the ringed-snake 

 {Trophidonotus natrix) the three longitudinal rows of spots in the 

 adult correspond to the positions of three subcutaneous blood- 

 vessels of the embryo. This work in some respects parallels that 

 of Loeb, but with the important difference that Zenneck finds the 

 pigment aggregating about degenerating vessels only, while Loeb 

 found that the circulation of the blood in the living vessel was 

 essential to the process. That this interesting observation, too, 

 merely throws light on a detail - — not a fundamental — of animal 

 coloration, seems quite certain. 



A paper by List 2 describes as universal for vertebrates the 

 relations between pigment and blood-vessels which were later 

 described by Loeb for Fundulus. His rather theoretical work is 

 based on the erroneous view that the pigments of vertebrate color- 

 patterns are carried into the integument by the leucocytes of the 

 blood. That his conclusions are wrong — particularly as applied 

 to birds — is proved by the results set forth in this paper, and by 

 much other evidence as well. 



Following this very brief statement and criticism of previous 

 work, we may perhaps be pardoned a concluding word concerning 

 the scope and limitations of the present contribution. The limita- 

 tions of the work here presented are, indeed, as obvious as they 

 are real, but to hold them in bolder relief for a moment may 

 prove of some slight service to those — if such there be — whose 

 eyes are ill-accustomed to the lights and shadows which play 

 upon this particular section of the borderland of heredity and 

 physiology. 



1. The origin and distribution of melanin pigment only has 

 been considered. This includes nearly all the black, brown, and 

 reddish-brown pigments of animals. It is clearly the prevailing 

 integumentary pigment of mammals, birds and many other groups. 



2. The birds only have been used as a basis of study. 



3. Very few of the actual groupings of melanin pigment in 

 the birds receive an immediate explanation through the processes 

 described. It seems very probable, however, that many com- 



1 Zenneck, J., " Die Anlage der Zeichnung und deren physiologische Ursache bei 

 Ringelnatter-embryonen," Zeitschr. wiss. Z00L, LVIIL, 1894. 



2 List, H. J., " Ueber die Herkunft des Pigmentes in der Oberhaut," Biolog, 

 Centra Ibl., X., 1891. 



