46 
GEOFFREY SMITH. 
proceeding to the proof of these facts, it may be mentioned 
that the object of Part 5 was to show that the injection 
of testis-extract had no effect on the comb-increase in the 
hen, normal control hens giving as wide fluctuations as the 
experimental birds. The greatest increase in any injected 
bird was 113 per cent.; the greatest increase in a control 
bird was 130 per cent., but it appears that this figure does 
not by any means indicate the limit of increase in a normal 
adult two-year-old hen, since the same bird has subsequently 
shown an increase of 201 per cent, within one month. 
The fact that the comb-increase corresponds to the egg- 
laying periods has been proved on two classes of birds : firstly 
in quite young birds laying for the first time, and secondly, in 
adult two-year-old birds. 
The curves shown in Nos. 1-9 (see Plates) record the 
increase in comb-area during 119 days of nine young Bankiva 
hens which were three months old at the beginning of the 
observations. The period when the egg-laying began is 
indicated on the curve by the upright lines, the line to the 
left showing the date of commencement, the 'line to the right 
the end of the period. It will be seen in every case that the 
curve takes a sudden and rapid rise just before, or coinci- 
dently with, the laying of the first egg. Curve No. 3 is seen 
to be a little irregular, the egg-laying period being broken 
up into three, a distinct fall in the size of the comb being 
recorded between the first and second short periods. 
Nos. 10 to 13 (see Plates) refer to adult two-year-old 
birds, the observations extending over a longer period and 
registering more than one egg-laying period. Nos. 10, 11, 
and 12 are of adult Bankiva hens, and they show very clearly 
the close correspondence between comb-increase and egg- 
laying as indicated by the upright lines. No. 13 refers to a 
white Leghorn fowl and the same correspondence is clearly 
shown. Similar records for three other white Leghorns 
might be given, but the evidence afforded by the thirteen 
curves depicted is amply sufficient to prove our point. 
It will be seen that the time of year has really nothing to 
