350 ME. E. DEGEN ON ECDYSIS. 



After Fatio's publication, the subject again la])sc(l, when it was reopened in 1877 

 with a short contribution by Gcrbe (23). To this author we are indebted for the 

 iirst allusions made to the genetic relations of the flight-feathers and their coverts. 

 Gerbe refers the student, at the beginning of his paper (which seems to have been 

 merely intended as a preliminary article), to some subsequent and more comprehensive 

 account of this subject. This appears never to have been published. This author's 

 researches do not extend beyond the flight-feathers and their principal coverts, as may 

 be seen on p. 290, I. c, pars. 9 & 10. 



The next important memoir which appeared is that of Dr. Gadow (20), which 

 throws much light upon the physical and chemical aspect of the feather-structure. 



Ignoring for the present a number of casual and disjointed observations which have 

 found their way into literature during this interval, we must look for the next really 

 important contribution towards a more orderly knowledge of the conditions deter- 

 minating the process of moult in birds to that made in 1896 by Dr. Wittmer 

 Stone (44). 



Apart, however, from the prominent part which this author has allotted to the main 

 quills and other feather-tracts of the body, the object of his researches principally 

 centres in an elucidation of the relationship of the moult with the seasonal changes of 

 the plumage in as great a number of families, genera, and species of the birds of 

 North America as possible. 



With the exception of the entries made on table iii., p. 116, of his work on the 

 relative condition of the smaller land-birds, no information is given about the covert- 

 feathers. To this work I have had to refer repeatedly in my arguments concerning the 

 different parts of the plumage. 



Soon after this there appeared in rapid succession articles by John Guille Millais 

 (35), "On the Change of Birds to Spring-Plumage without a Moult" (referring to the 

 Grebe and Dunlin, but principally the Sanderling), and that by Dr. Chapman (13), 

 also on the Dunlin, the Sanderling, and the Snowflake. 



In another paper in 1897, this latter author (15) also made some remarks in reply to 

 Dr. Chadbourne's (11) exhaustive account of his observations on the "Spring 

 Plumage of the Bobolink." The last-quoted pa])ers have mostly dealt with the question 

 of colour-change with or without moult. 



Works with a more direct bearing upon the morphological features of the wings of 

 birds, and especially their coverts, are those of Goodchild (27), Wray (46), Gadow (21), 

 and Pycraft (38). More recently, again, Chalmers Mitchell (12) and Pycraft (39) have 

 made attempts to arrive at a flnal solution of the question of Diastataxy. In these two 

 papers, which appeared contemporaneously, the interest attaching to the wing-coverts 

 as the most important factors was accordingly renewed, and is proportionate in amount 

 to the different standpoint taken up by these two last-named authors. 



