PLATE 7 
EXPLANATION OF FIGURES 
21 Illustrating the rudimentary down feathers at birth, and the growth of 
the flight and contour-feathers from birth to climbing stage. 
a, Down feather-tubes from dorsal tracts of cuckoo at birth; bird No. 4, 
nest No. 3, July 25. b, Down tubes from femoral tracts from bird a few hours old. 
Bird 1, (shown in fig. 1), nest 3. Aug. 1. c, The same, dorsal tracts. Bird 1, 
nest 3, July 25. d, The same from femoral tracts, showing long flagellum of 
rudimentary down; bird 1, nest 2; beginning of 6th day, in quill stage. Aug. 6th. 
e, Feather-tubes from abdominal tracts from same, f, Feather-tubes from 
abdominal tracts; bird 4 (quill stage); nest 1, seven days old. Aug. 1. g, The 
same: bird 2, nest 1; 6th to 7th day, Jul}' 27. h, The same, showing feather 
released by removal of horny sheath entire; same bird and date, i, Two prima- 
ries at birth, showing down-tubes; bird 4, nest 1, July 25. j, Primaries from 
cuckoo in complete quill stage; the smaller from bird 1, nest 2; 6th day, Aug. 6; 
the larger from older bird, k, The same from bird in climbing stages; No. 4, nest 
l;7thday. Aug. 1. 1, Thesame;bird 2, nest 1; 7daysold. July 27. m, Primary 
from bird in climbing stage, showing feather released for two-thirds of its length; 
bird 2, nest 2; 8th day, cUmbing stage. Aug. 10:10 a. m. n, Tube from femo- 
ral tract; bird 2, nest 1; 7th. day. July 27. o, Tail-quill; bird 2, nest 2; eight 
days old, in climbing stage. Aug. 10. p, and q, Feathers from femoral tracts; 
bird 2, nest 2; 7 days old. Aug. 9. r, Cast off horny sheaths, from litter of 
nest, bearing down-tubes at tips, s, Wing-coverts; bird 2, nest 2; 7 days old; 
10 a. m., Aug. 10. t, Feathers from femoral tracts; the first to appear; bird 2, 
nest 2; 6 days old. Aug. 0. All in full size, and as plucked from bird. 
