PTEKYLOGKAPHY 



FIRST PART. 



GENERAL PTERYLOGRAPHY. 



PRELIMINARY REMARKS. 



THE information which I propose to communicate in the present work, the result of many 

 years' careful investigation of the subject, relates to a department of zoological observation which 

 appears to me to be of the highest importance, but which has never been treated as its great 

 significance deserves. Although the general laws of position of the dermal coverings of animals 

 have occasionally been discussed, no observer has taken the trouble to say anything more about 

 them than may be learnt by a passing glance. This, however, only shows that the bodies of 

 most fishes and amphibians are usually clothed with scales arranged in rows, and generally of 

 equal size, and that mammals and birds have been endowed with a similar but more external 1 

 horny covering. From the universal and homogeneous distribution of the scaly clothing of the 

 former, it was concluded that the arrangement and composition of the plumage of birds was 

 similar ; and thus, misled by external appearances, observers have overlooked one of its peculiarities, 

 certainly not the least important zoological character of this group of animals, which appears to 

 present but little variety in its subordinate differences. The desire to analyse this remarkable 

 uniformity in external form (which has driven the majority of zoologists and even the greatest among 

 them to adopt a defective classification of birds) by a careful and thorough study of that class of 

 animals, and to ascertain the true multiplicity of form in them, has been my guiding principle from 

 my youth in my ornithological investigations, and the discovery of the laws of the relative position 

 of the feathers which I have now to communicate, is one of the interesting systematic results 

 with which more than thirty years' occupation in the study of birds has made me acquainted. 



1 I have called attention on several occasions (e. g., in my ' Naturgeschichte,' p. 664) to the 

 essential difference in the covering of cold and warm-blooded animals ; in the former all such structures 

 are bones, which lie in pouches of the epidermis, but beneath it ; in the latter, they are horny processes 

 which project from the pouches. B. 



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