CHAPTER XX 



NOTES ON A FEW EMBRYOS 



I 

 A NEARLY MATURED EMBRYO OF THE DUSKY NIGHTHAWK 



Caprimulgus nigrescens ( Cab. ) 



PTERYLOSIS 



The several feather tracts are marked by long violet- 

 brown down sheaths. The sheaths of the wing, tail, tarsus 

 and femoral tracts are more advanced than the rest, averag- 

 ing about 4.5 mm. in length, and are more thickly clustered 

 than at any other place on the body. The rectrices with their 

 upper and under coverts are well developed and long. The 

 femoral tracts consist of several rows of long sheaths which 

 grow close together and make a large patch. These, together 

 with the rectrices and their coverts give the embryo a very 

 heavily feathered appearance on the posterior portion. The 

 feathering of the leg and the especially heavy feathering of 

 the tarsus, which is feathered in front with a thick tuft of 

 sheaths that extends to the base of the third toe so that the 

 tips of the sheaths extend past the second joint, add to the 

 heavy posterior coating. (Fig. 109.) 



The wing sheaths are equally as long and as thickly 

 patterned as the others. Those on the forearm in particular 

 are very numerous, the secondaries being buried beneath a 

 thick mass of coverts, which, though the rows are a trifle ir- 

 regular and rather indiscriminately placed, are all heavily 

 represented. The primaries have single coverts with a sparse 

 scattering of sheaths above. 



The dorsal tract is at no point very dense. Over the 

 pelvis it consists of a triple row of rather closely placed 

 sheaths. Above the sacral region the middle row disappears 



