140 Trans. Acad. Sci. of St. Louis 
reactions are exact opposites in expression, involved a curve 
which dropped from the first to the zero point and then rapidly 
ascended to the expression of the latter. Thus between the two, 
lessened expressions of either reaction would result, with a cur- 
ious hiatus midway in which the incubating bird would allow 
an intruder to approach closely and then leave without an 
expression of either. Experimental flushing of an incubating 
bird from a blind showed that the bird, in one case, would give 
distress simulation if flushed in an interval that was less than 
two minutes from the time of her return; but would give casual 
abandonment if flushed after an interval of five minutes. (See 
Table 14.) A female Lark, shortly after being forced from a 
nest, would express her agitation by aimless ground pecking, 
and, to be sure, would eventually be driven by the incubation 
urge to return to the nest even though an intruder might be 
much nearer than the distance when the nest was originally 
abandoned. This complex of instincts involved both the urge 
to incubate, and the urge to protect. The instincts to protect, 
by whatever method, would all be overshadowed in time by the 
instinet to incubate. 
F, The young. 
1. Hatching. With the exception of those nests of early 
April, in which incubation began before the set was complete, 
all young hatched within an hour or two of each other. The 
young are fed within an hour or two following hatching. 
2. Feedings. In most cases the male assisted the female in 
feeding the young. In carefully observed cases he visited the 
nest less often, but brought greater burdens and fed more 
young at a visit than did the female, The total number of 
feedings during one day (April 30, 1926) was 117. An exten- 
sive summary is presented in Table 17. 
3. Food of nestlings. Observations of the adults and dissec- 
tion of a few nestlings showed that some vegetable matter 
(weed seeds) is fed in early spring, but that even in March 
most of the food is animal matter. Later in the season grass- 
hoppers become conspicuous in the diet. The adults dig UP 
both eutworms and earthworms. 
4. Reaction of adult Larks with young in the nest. The 
male shows solicitude for the nest and its contents for the first 
time after the hatching of the eggs. His solicitude is restricted 
