GROWTH AND DEVELOPMENT 85 



It may be seen that at hatching only seven primaries and nine secondaries are present, 

 although the full complement comjjrises 10 and 15 respectively. For the purpose of this dis- 

 cussion the primaries are numbered with the first at the outermost portion of the wing and 

 the tenth closest the body. Among the secondaries, the short axial feather adjacent to the 

 tenth primary is designated as 1 and the others numbered consecutively toward the body. 

 This order of numbering is most generally followed in ornithological literature although a 

 different system is frequently followed in discussions dealing with domestic fowl. Among the 

 primaries, development progresses in a regular order from number 10 toward number 1, 

 while among the secondaries the pattern is not as regular. The succession here seems to run 

 in the following order: from 3 to 1.5 consecutively with number 2 appearing simultaneously 

 with number 5 and 1 appearing simultaneously with number 6. 



One Week 



By the end of the first week considerable growth ma) be observed in the flight feathers. In 

 addition to the seven visible at the time of hatching, numbers 1 and 2 are usually just protrud- 

 ing from the skin. The longest primary of the folded wing extends back to the tail fuzz. In 

 addition, three or four scapulars are present on each side where the wing joins the body. 



Two Weeks 



By this time growth of the ju\cnile ])rimaries number 10, 9. and 8 has been completed as 

 evidenced by the absence of blood in the base of the quill where it enters the skin*. The 

 first primary is slightly longer iIkui the overlying greater covert. The axial or number 

 1 secondary is half grown, while luiiiilx-rs 2 to 1 1 are from two-thirds to one-quarter devel- 

 oped and number 12 is in the |>iii stage. 



Ten or more scapulars are now apparent on each shoulder and feathers are visible on the 

 sides. Pinfeathers with the downy tufts of the natal |)luinage still appended are present 

 in the region of the lower nape, back, rump, tail, belly, and (lank. Two or three pinfeathers. 

 which later develop into the crest, may be discerned on the crown. The lower wing coverts 

 are still obscured bv down. 



Three Weeks 



The juvenile primaries number 10 and 9 have already dropped out and are being re- 

 placed by adult feathers. The tip of number 10 is exposed and slightly longer than the base 

 of the quill. Number 9 cither may be missing or the tip barely showing through the skin. 

 Of the juvenile flight feathers still present, growth is complete in primaries number 8, 7 and 

 6, as is also true of secondaries number 3 and 4. 



The greater wing coverts are fully developed and the upper surface of the wing is well cov- 

 ered except in the area of the web. This latter region is sparsely covered with down with no 

 pin feathers in evidence. The edge of the web. however, is covered with three rows of feath- 

 ers, growth in the first row being complete. 



The up])er part of the head is completely covered with pinfeathers from the base of the 

 mandible back to the nape. That portion below the eyes and under the chin is still in down. 

 Juvenile feathers have appeared on the back of the neck merging with the scapulars. The 

 complete bridge of feathers across the back has been acquired at this age. The feathers 

 on the sides have attained sufficient length to cover a portion of the belly. This latter re- 



* After growth is cnniplele a t)iiill becomes transhireiil and dry. 



