136 



Degeneration in the Ostrich 



regular succession of the plumages — chick, juvenal and adult. They 

 are also found on chicks at hatching or even before hatching, showing 

 that the particular stages reached are germinal and not ontogenetic 

 productions. 



e t g h i 



Fig. 2. Stnges in degeneration of a feather. The feather first undergoes a gradual 

 reduction in size ; the central shaft then breaks up into two or three parts, as in 

 c and d ; the imperfect shafts disappear and a simple tuft of barbs with barbules is 

 formed, e ; these undergo a gradual reduction and loss of barbules until only one or 

 two hair-like barbs remain, / to /. 



Some birds afford evidence that a loss of coverts is beginning at the 

 distal end of the row also. Usually no under-covert alternates with the 

 first and second remiges (Fig. 1), though such would normally be ex- 

 pected. Occasionally however two, three, or even four alternations are 



