504 
Bulletin No. 162.—1915. 
of the birds to their greatest capacity has not been consistent with 
obtaining data on the point at issue. We still, however, allow the 
birds to incubate a day or two beyond the normal period unless it is 
certain that the embryos are dead, so that from our routine experience 
together with the data in Table VIII, we are able to state positively 
Table t ill. —Length oj time eggs icere incubated when they did not hatch: counted 
from time of laying of second egg. 
(The numbers are those of the nestings concerned; each number represents one 
record.) 
Days 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
11 
7551 
10 
688 1 
9 
558 
529 
•E 
8 
737j| 
716 
O 
- 
{ 
746 
512 
. . . ( . 
va_ 
o 
(I 
704 
741 
653 
505 
533 
(-1 
JD 
5 
445 
494* 
695 
464 
729 
£ 
zs 
4 
757 
425 
422 
4021 
400f 
335 
475 
595f 
498 
357 
675 
z 
3 
605 § 
470*t 
477 
761 
426 
330 
674 
714 
2 
476 
551 
386 
379f 
267 
309 
316 
406 
703 
465 
1 
308 
305 
54 It 
332* 
241 
298 
180 
280 
304 
384f 
381 
3311 
Totals 
Q 
4 
3 
o 
pm 
i 
6 
11 
5 
8 
5 
3 
2 
♦Record incomplete. 
tOnly one egg laid; calculation made from time second egg should have been laid. 
JOne squab hatched, but died soon. 
§Adopted squabs from another nest. 
UPossibly a day or so less. 
that it is very infrequently that the birds cease incubating volun¬ 
tarily by the eighteenth day after the laying of egg B, in case they 
are allowed to retain unhatched eggs. An inspection of the Table 
shows, as a matter of fact, that under the conditions specified more 
birds stop incubating at 23 days than at any other time, and that the 
number of records falls off from this point in both directions as 
regularly as could be expected with such small numbers. The 
