Jeffries.] 212 [February 7, 



epidermal coats. In 1840, Burmeister (9), in the first part of Mt- 

 zsche's Pterylography, explained how the feather-parts were 

 made of cells, but did not show the origin of the cells or their 

 morphological nature. In 1869 and 1870 Studer (13, 14) published 

 two papers on the growth of feathers, showing them to be formed 

 from epidermal cells, but paying little attention to the layers of 

 the epiderm. In 1870 Samuel (15) published a valuable article on 

 the development of feathers. This author, however, studied 

 their growth from a physiological standpoint and passed over 

 anatomical detail. Dr. Samuel's statement that castrated birds, 

 capons, do not moult is ambiguous. It seems to be true that 

 capons do not moult large numbers of feathers at one time; on 

 the other hand, the old worn feathers are removed one by one 1 . 



In 1873 Studer (16) published his first paper on the development 

 of feathers, and gave us by far the best description we have. 

 The work will be repeatedly referred to later on and must not 

 delay us here. 



In 1877, Kerbert (4), in an article to which we shall refer fre- 

 quently when considering the growth of scutae, made the follow- 

 ing statements : First, that the shaft of the penguin feather is 

 in reality no shaft, but consists of agglutinated barbs; second, 

 that the feather pulp is permanent in this group. 



In other words he saw in the feathers of penguins a link between 

 feathers and scales. 



Unfortunately, as Studer (17) showed, in 1878, neither of these 

 statements is correct. The shaft is a true shaft, just as much 

 as that of any other bird, but is more or less flattened. Normal, 

 though sparse, barbs are also present. Lastly the pulp aborts in 

 precisely the same way as in other birds. Thus the supposed 

 link connecting feathers and scales proved too weak to support 

 its own weight. In the same paper Studer also described the 

 formation of the aftershaft in the Cassowary. 



Passing now to the development of feathers we find the follow- 

 ing points of interest. 



First, the great complexity of the final structure, especially as 

 regards wing and tail feathers. 



The minute structure of these vary in the different groups of 

 birds, as I have myself observed, and has, I believe, been pointed 



!This statement is made on the word of the poultry growers in the vicinity of Boston; 

 I have been unable to study the point. 



