392 MR. E. DEGEN ON ECDYSLS. 



The latter, wliicli I refer to throughout as Group II. (comprising remiges I., II., II 1., IV.), 

 consequently fornas the other " point extreme " of which Gerbe speaks. We have 

 disposed, then, of two groups, whose remiges severally tend in the same inward direction 

 for their moult. 



This leaves us with a balance of three flight-feathers situated between the proximad 

 limit of Group II., viz. remex IV., and the distad limit of Group I., viz. remex VIII. 

 The moult, however, of the remiges of this centrally situated, or Group 111., jjroceeds 

 in. an opiwsite direction (that is, in inverse order of their numbers), namely by beginning 

 with remex VII., then VI., and by closing it with V. In the chart (Table II.) prepared 

 for the chronological movement of the remiges (further see diagrs., Plate XXXVI. 

 &c.), their alternate directions of moult are indicated by darts, pointing in the respective 

 direction of their renewal. 



In this way the order of the moult of each flight-feather itself becomes a definite 

 unit of the group to which it belongs. 



Similarly, as has been explained, each group itself becomes a definite unit in the 

 cubitus as a whole. 



Consequent upon the synchronous appearance of two or more group-integers, the 

 numerical order in the replacement of the flight-feathers within the cubital portion as 

 a whole breaks up. 



i The Tectrices. 



The renewal of the wing-coverts presents some notable deviations from that of the 

 flight-feathers. 



Whereas the latter adopt the ultimate plan of renewal in sections immediately in 

 their first perennial moult, the wing-coverts do not follow this same principle so 

 soon, except by means of a series of transitory stages. These latter form a system of 

 complexity in which two entirely different morphological features seem to mingle with 

 each other: the one an early horizontal or diagonally longitudinal, and the other, 

 later one, consisting of a transversely diagonal one for renewal. 



As might have been noticed, a certain amount of difficulty occurred in tracing out 

 the two systems of development. However, in following up step by step the order of 

 renewal of the coverts — providing an extensive series of individuals be consulted on 

 this point — all the conditions in the physiological process of their perennial moult 

 may be found for discriminating between the various phases which produce this state 

 of complexity. 



But in order to better comprehend the degrees of complexity attending this interesting 

 morphological question, it has become necessary to refer to some of the statements 

 made on the subject of those writers particularly whose works have appeared in more 

 recent years. 



The observations made by Gerbe (23) on the simultaneous shedding of the principal 

 coverts for the hand-portion of the wing have been described fairly correctly by 



