326 TROPICAL WILD LIFE IN BRITISH GUIANA 



A third tract of large development is the femoral tract. 

 Here the sheaths are nearly as long as those of the spinal 

 tract and pigmented. A slight darkening and lengthening 

 of the scapular tracts may be observed in the young embryo 

 and there are a few long sheaths in the occipital region which, 

 in the later period of hatching, become very long and promi- 

 nent. In the space between the eyes there are two single 

 rows of long, dark sheaths running along the eye grooves. 

 All inferior tracts are indicated only by papillae, there being- 

 no noticeable pigmentation or lengthening. 



Ill 



Varied Streaked Flycatcher Ejnjndonomus varius varius 



(Vieillot) 



PTERYLOSIS 



Unfortunately I have been able to seciu'e only two em- 

 bryos of this bird, both of which are about half developed, 

 though one is apparently a few hoin*s more advanced than 

 the other. Only small papillae are present, there as yet be- 

 ing no sign of pigmentation. Some of the papillae, how- 

 ever, are more prominent than others, and, from the exam- 

 ination of a newly hatched chick, I find that they are the 

 ones that develop into the main down sheaths. 



The positions of the papillae tracts are very similar to 

 those of Pitangus sulpJniratus of a slightly more advanced 

 stage, except in regard to the growth of the rectrices. In 

 the present bird these j^apillae may be seen in their proper 

 place with a corresponding row of coverts above, both show- 

 ing the tiny specks at their tips which are the first indica- 

 tion of pigmentation. The rectrices, themselves, are much 

 larger than their coverts. Directly the opposite is the case 

 of P. sulphurafus in which the coverts develop first, attain- 

 ing a good length and a dark pigmentation before the true 

 rectrices appear plainly as papillae. In the young chick of 



