398 MR. E. DEGEN ON ECDYSIS. 



affected earliest, and siiruiUaneously with the coiTespondiiig rows of the spinal tract; 

 the internally and externally situated ones which compose these branches begin to moult 

 somewhat later, about the same time as the renewal of primary reraex III. ; this is also 

 the case witli the lateral rows of the thoracic portion of tlie spinal tract. The moult 

 for the feathers of this tract on this part of the body sets in most vigorously, and is 

 achieved at a comparatively earlier period than that of the dorsal main stem. 



Closely allied to the distal rows of its humeral branch are the feathers which 

 compose the " Parapterum." Only a narrow space separates the two. The feathers 

 of the latter take up the moult from the humeral branch, and in younger birds are 

 replaced by synchronous appearance, whereas in older individuals they are renewed in 

 more regular sequence from within outwards. 



The more marginal branch spoken of, and entered also in Chart (Table VI.) as 

 " clavicular," follows the same principle for the moult of its feathers as that which 

 applied to the former branch. Its distally situated rows on the underside of the wing 

 establish a connection with the " Hypopteron," from which it is but slightly separated 

 also. The feathers of the Hypopteron, which are a somewhat rudimentary set (being of 

 a filo-plumaceous structure), begin moult — which is always a simultaneous one for 

 them — later than those of the Parapterum, their appearance corresponding with the 

 renewal of primary V. 



The Inferior or Ventral Tracts (Pterylse gastrsei). 



Commencing with the chin, and covering the throat in one homogeneous mass, 

 together with the head and sides of the neck, with which portions it coalesces, this 

 tract divides . itself into two stems in the gular region, which descend in a laterally- 

 curved line towards the anal region, without, however, reaching the orifice. These 

 two stems enclose the apteriimi mesogastrceum of Nitzsch (p. 34, I. c.). Excepting the 

 portion of the throat mentioned above, its rami may be further subdivided into 

 "pectoral" and "inguinal" portions respectively. The former are of considerable 

 width, and consist of about from eight to ten longitudinal rows of feathers in their 

 broadest parts. These send off' the lateral extensions, backward and outward, referred 

 to by Nitzsch (cf. p. 27, I. c.) as pteri/lce laterales, more prominently perhaps in the 

 species under examination than in those Passerine forms referred to by the latter author 

 (cf- PP* '-^^ ^ ^^> ^- ^•)- These small ramifications set off distinctly enough imme- 

 diately in front of the portion which forms the greatest expanse in the double tract 

 just below and posteriorly to the arm-pit. 



At a place slightly in advance of the junction of the latter with the main pectoral 

 portion is the principal centre from which the moult proceeds longitudinally back- 

 wards, and to both sides of the tract, by renewing every alternate feather, sometimes 

 overlapping two feathers in either direction. The inner rows of this portion moult 

 with great rapidity during the earliest stages of the complete feather-change ; whilst 



