THE PROBLEM OF ORGANIC DEVELOPMENT. 



189 



single line, supplemented by la and lb at the bend of the wing. The next row (2) 

 consists of the 5 black-tipped feathers, which we saw emerging at 17 days; and the 

 third row of 7 feathers has been added in the interval. 



It is about this time, or a few days earlier, that the fourth row of coverts (iv) 

 after having been overgrown by the feathers of the oblique tract, is molted. From 

 this time onward, the remaining rows of coverts fall one after the other, the molt 

 in each row proceeding from the inner end outward. 



In this stage, then, the scapular tract excepted, we have only original feathers 

 in sight, the whole oblique tract consisting of first feathers. The four rows of coverts 



Text-figure 33. 

 Same as text-figure 32, age 38 days; drawn by Hayashi, Aug. 1899. X2. 

 Another row of dark-tipped feathers, with wider tips than the earlier oblique streak, are growing over the second 

 row, and above we see three feathers that have advanced farther. A few (four) feathers in scapulars are wide-tipped 

 with black. Arrangement: 1 shows the first row of later feathers with narrow light tips. 2 and 3, the second and third 

 rows of narrow black tips. 4, the fourth row of wider black tips (about complete in number). 5, feather of fifth 

 row; overgrowing the second (//)— light edge— row. 6, a feather of the sixth row, next to scapulars, reaching a little 

 over the second (//) light row. 7, a feather of the seventh row, in line with first row (I) of light-edged feathers, s'", 

 later scapulars with very wide black tips. Other designations as in figures of 17-day stage. Behind the first two 

 rows of black-tipped feathers we are to have 4 rows of black tips— that is, twice the number of light-tipped rows. Be- 

 ginning with the first row (narrow light tips =7) we have 7 rows which take the place of the 4 original rows. 



(i to iv) are each to be replaced by black-tipped feathers. Thus the field behind 

 the lesser coverts is to be occupied by seven rows of feathers, of which three are 

 original and four are replacements, following the molt. 



Ten days later (text-fig. 33) , we find four of these rows completed ( 1 to 4) , and three 

 (5 to 7) represented each by a single feather. Most of the lesser coverts have been 

 cast, and 6 black-tipped feathers are here in sight. The later feathers have every- 

 where the wider and blacker tips. In the scapular region 5 of the later feathers 

 (s'") are readily recognized by the greater width of their black tips. The original 

 tertials are still in place, and they give us another series of grades running from the 

 earlier pale-tipped to the later black-tipped condition. 



