NOTES ON EMBRYOS 327 



E. variiis, however, we find that, hke the other species, tlie 

 coverts exceed the rectrices in length and development, 

 though the latter are present and more advanced than in the 

 other. 



The sacral cleft of the spinal tract is slightly wider and 

 longer in E. varius and extends beyond the sacral region for- 

 ward into the scapular area. In the newly-hatched bird the 

 difference is a little more marked, the arms of the tract being 

 narrower than P. siilphuratus. In other particulars the 

 pterylosis of the two birds is similar. 



