258 



ME. W. P. PTCEAFT ON THE 



In the nestling, however, they were readily visible in the form of somewhat 

 conspicuous packets, one at the base of every contour-feather. Their examination under 

 the microscope revealed some very interesting facts concerning the nature and history 

 of these curiously modified feathers. As will be seen in fig. 5, each at this stage 

 consists of a sheath investing a number of rami, and a rhachis, clustered around a column 

 of " pith-" cells. Before the full growth of the feather is attained everything save the 



Fis. 4. 



Fig. 5. 



Fig. 4. — The distal end of a filojjlume of jS'co^js leucotis. 



Fig. 5.-Filoplume of a nestling Siuotuto mnicularia. The part marked / is all that remains in the adult, and 

 forms the filoplume ; T, the transitory radii ; j*, pith-cells. 



main axis is thrown off. This remains as the typical filopkune of the adult. Dr. Gadow 

 (4} remarks, "their development shows them to he degenerate, and not primitive 

 feathers." 



Neossoptiles.—Ks is pointed out in another part of this paper (p. 253), two kinds of 

 neossoptiles must be distinguished — (1) pre-pennse and (2) pre-plumulae. 



Pre-penn£e * can be readily distinguished from pre-plumulce only under the microscope. 

 The component rami of these umbelliform down-tufts, being continuous with those of 

 the definitive contour-feathers, are broken up and spread out horizontally as soon as 

 the tips of these latter have burst through the sheath by which they were enclosed. 



* The pre-pcnna3 described arc those of Sptotyto mniculana. 



