100 Trans. Acad. Sci. of St. Louis 
19, 20, 21, Figures 12, 13, 14, 15, 16, 17), and a brief summary 
only will be given here. There are but two or three measure- 
ments that have significance, as far as I can see, and these only 
have been considered, i. e., weight, total length, length of tail 
and length of flight feathers. 
The weight of the egg near hatching averaged 2.85 grams. 
As might be expected the newly hatched Larks were a little less 
than this, but so promptly are they fed that very few first 
weighings were made before the young were able to show a 
100 
’ 
rest}ing lees 
“ pestiing lose 
of plus egg ices 
egg i088 
March April wey June dely 
Figure it 
Fig. 11. Loss of eggs and nestlings of the Prairie Horned Lark dur- 
ing the 1926 nesting season at Evanston, Ill., in per cents per 
considerable increase over the ege weight. Growth is uniform, 
both in weight and length, until the approach of the seventh 
day. At this time the rapid, very general unsheathing of the 
feathers causes a check in weight growth. Indeed a loss is shown 
where weighings were made late on the seventh day and early 
on the eighth (see Figure 13). The Cowbird nest-mate of one 
Lark nestling was still in pin-feathers at this period and does 
not show this straightening in the curve (see Figure 15). The 
April nestling developed so slowly that this straightening in the 
curve in its case (see Figure 12) is not apparent. As might 
