394 ME. E. DEGEN ON ECDTSIS. 



Tlie great importance which attaches to the covert-feathers in helping to clear up 

 outstanding questions connected with the evolution of the organ of flight was fully 

 recognized by Mr. Pycraft (39), who has approached the subject of the origin of 

 Diastnta3;y from the point of view of Embryology. In the course of his description 

 of the "Embryo Wing" (see p. 239, I. c.) he says, for instance: — "The movement of 

 the remiges is in all cases accompanied by a corresponding movement on the part 

 of the coverts associated thorevvitli, from the post- to the pre-axial border." 



And continuing, he says: — "The result, when the wing is viewed as a whole, 

 seems to show that a process of ' faulting ' has taken place, &c., &c." This process 

 of faulting or shifting he, moreover, supports by an ably devised diagram (see 

 p. 239, I. c). 



It is I'eally the first indication of a transverse rearrangement of the rows at this early 

 stage of development. That it is a totally distinct feature from the longitudinal 

 principle of feather-supply is equally endorsed by this author, who initiates, on p. 238, 

 the paragraph treating of the subject by the following words: — "In all wings the 

 feather rudiments appear first along the post-axial border of the wing ; those repre- 

 senting the remiges and their major coverts appear simultaneously, and sometimes 

 together with very faint traces of one or more of the pre-axial rows representing the 

 median and minor coverts." And further : — " The change takes place, however, 

 generally at the close of this phase of development." 



Now it is this " faulting " precisely on which Goodchild in his researches has laid so 

 much stress, and which has supplied this author with such a solid basis for his obser- 

 vations on the coverts of the cubitus. Further evidence of a transverse character he 

 has clearly also shown to exist in the alternate imbrication of the members of certain 

 series of coverts, which is so conspicuous a feature in a great number of families 

 of birds. Similar indications of this principle may be found to exist also in the 

 shape of the permanently shortened coverts which mark the various sections of this 

 portion of the wing for some families of birds (Degen (16), p. xxiii). Their places 

 almost exactly correspond with what we have learnt through the conditions under 

 which they moult. 



The appearance of a first set of wing-feather-plumage is an endowment of secondary 

 origin. It is the common bondage for all Carinate birds. In the Chenomorphm, for 

 example, this early ontogenetic mode of feathering is repeated more or less in every 

 moult [antea, p. 366) for both portions of the wing. 



In more highly organized forms, however, this latter mode is confined merely to the 

 very young individual on the cubitus, in which, with every succeeding annual moult, 

 the transverse character of primitive origin comes into prominence. 



The latter reveals itself also by the moult of both the flight-feathers and the coverts 

 on the metacarpo-digital portion in some families of the Picarice (Kingfishers) ; 

 whereas in the Passeres, whilst being merely concealed by a chronological difi'erence 



