352 ME. E. DEGEN ON ECDYSIS. 



Examples like the foregoing will therefore show the significance of the remarks 

 made on this head. 



Without doubt a somewhat similar cause must have been responsible for the 

 greatly contradictory results obtained in the case of the " Bobolink," in the researches 

 made into the moult of this migratory species by Dr. Chadbourne (ii) on the one 

 hand, and by Dr. Chapman (15) on the other. An inquiry into the geographical 

 rauge of Dolichoni/x oryziwrus discloses the fact that this species extends from the 

 north of Carolina, through Texas and Mexico, into the tropical belt of South America 

 north of the Equator. The chances, therefore, are that Dr. Chadbourne's birds, having 

 been procured from a dealer, as he himself states, may have got into the latter's 

 hands from entirely diiferent districts, and probably also from the extreme limits of the 

 geographical range of this species. 



The other plan upon which to conduct the study of the moult, namely, that of 

 using the dried material of cabinets, has some equally serious drawbacks. It rarely 

 happens that a complete series for all the stages forms part of a general collection 

 {cf. Allen (i), p. 42). Useful no doubt, as this type of material proves to be in 

 providing supplementary evidence in doubtful cases, the different object, however, for 

 which it has been gathered does not, as a rule, recommend it for this purpose {cf. also 

 Wittmer Stone (44), p. 109). 



My own method (and for which I have good reasons for reliability) has been that of 

 procuring, at regular intervals of one week, several specimens of the species named, 

 from the first signs of moult appearing, throughout the whole period of feather- 

 change. 



By this means the birds can be examined at leisure while yet in a perfectly fresh 

 condition. Their further preservation in alcohol is an additional advantage for re- 

 sulting them at any time when required for a comparison one with another. 



This inquiry was conducted on -32 individual specimens, of which number 21 were 

 were males and 11 females. (See Table I. parts a Sc b.) 



Of this satisfactory series of specimens on which to base these observations, 27 enter 

 into the descriptions. The remaining 5 specimens, rios. 28-32, which represent those 

 received at the end of the moulting-season, may, though they still show traces of 

 incomplete renewal of a few of the feathers of the trunk, for all practical purposes be 

 considered to have acquired the fully developed garb. 



The first step taken in the present investigation has been that of measuring singly 

 each flight-feather in both w'ings of all the individual birds. This procedure, perhaps 

 unnecessary at first sight, has had the advantage of not only demonstrating the 

 numerous individual difierences of lengths of these feathers in a given species, but has 



