1 66 



OSCAR RIDDLE. 



or rather, different forms of the same defect and I shall first 



give a description of the nature of the defects, and later consider 



the question of their extent and cause. 



Defects in Adult Morphology. In the adult expanded feather, 



I have found five types of defects in structure. In Fig. I, a is 



shown the first type. There is in 

 this case a sharply defined area ex- 

 tending entirely across the feather- 

 vane, in which there are no, or 

 very few, perfect barbules. A 

 cross-section of the feather at this 

 point would show only shaft and 

 barbs. One such area in the entire 

 length of the feather was one of the 

 types described by Strong. I find, 

 however, an abundance of cases 

 where such areas occur at regular 

 intervals practically throughout the 

 length of the feather. This regu- 

 larity in the spaces separating the 

 defects, indeed, furnished the clue 

 to the nature of the latter. It will 

 be seen that these areas cross the 

 Feather from a poorly barbs in such a way as to form 



nourished chick showing abnormal!- a l mO st a right angle with them. 



ties. (?, abnormal area ; b, ' funda- , . ,. . 



f ,,,,,, .,. The same thing is true of the other 



mental bar (a day s growth) ; c, 



constrictions ;</, region in which de- types of defects and argues for 



fective lines showed plainly in this their standing primarily all for the 



feather. ( V 2 - ) 4.1 



same thing. 



The second type represents the greatest extreme to be met 

 with among these abnormalities. The feather in the abnormal 

 region has been reduced to shaft only ; both barbules and barbs 

 are gone. The second of the defects described by Strong evi- 

 dently belonged to this type, though he states that there was no 

 shaft present in his material and that its place was taken by a 

 small cylinder of fused barbs. I have not seen just such a 

 structure as he describes ; but it is rare and doubtless is to be 

 regarded as a sort of record of the very severest conditions which 



FIG. i. 



