400 MR. E. DEGEX ON ECDYSIS. 



The Eectrices and their Coverts. 



The tail-feathers are replaced in a perfectly regular order from within outwards, as 

 are also their coverts, both dorsal and ventral. These coverts consist of two rows 

 each, equivalent to the major and the median coverts of the remigcs. 



The first or innermost pair of rectrices — of which it is sometimes the left, or as in 

 some individuals the right side, which moults first — is renewed at the time of renewal 

 of primary remiges III., IV., and V., or the triplet marked c, d, e (see also diagram, 

 Plate XXXVI., and Tables I. & VI.), as has been pointed out. 



About the time of renewal of the 5th primary, the second innermost pair of rectrices 

 takes up the moult, generally before the first is completed, and, with tlie next remex 

 in moult (viz. primary VI. ), the third pair follows suit, and so on; the last and 

 outermost sixth pair coincides generally with the two outermost metacarpo-digital 

 remiges IX. and X. 



Frequently there are as many as three pairs of tail-feathers to be seen in various 

 stages of graduated length of renewal, but, as a rule, there are not more than two. 

 The former condition occurs in younger, whilst the latter is the case for older indi- 

 viduals. Their dorsal coverts take up the moult somewhat later than their ventral 

 ones, which latter are amongst the first feathers to renew of the wliole plumage, as 

 may be seen, by their relative order to the rectrices, at the bottom of the Chart 

 (Table VI.). 



IX. — Conclusions. 



Having, iu the preceding pages, described the chronological behaviour of the 

 feathers during the moult of the individual, and further shown, with the help of 

 diagrams and tables, the relationship of their development to one another, by paying 

 special attention to the principal feathers, I can now proceed with the explanation of 

 my views with regard to the manner in which they reflect the phylogenetic conditions 

 of the archseornithic type from which the wing of the modern bird has been evolved. 

 For this purpose it becomes inevitable to refer again to the details of the theory 

 propounded in the pages of my former work (i6) and notably so to plate i. fig. 3, 

 I. c, for the views there brought forward. 



The present investigation gives me no cause for materially altering the funda- 

 mental plan laid down in the former paper, other than two slight modifications. The 

 first and principal one, referred to already under the part headed " Ala spuria," is the 

 result of the additional discovery of the inverse order in the shedding and eventual 

 replacement of the pennce alares of this portion, as affording us a likeli/ key to its further 

 solution. The other point is one of a merely subordinate character, and I propose to 

 allude to it later on. 



Immediately on entering upon the question, our attention once more gets directed 



