Cl. H. F. Nuttall 
several thicknesses of camera cloth (black, lined red) during the half-hour 
feeding periods, when my laboratory assistant left the dark room. The lice 
were exposed to diffuse daylight for only a few minutes as nits (when the 
parents were removed), and once for 3 4 minutes when the box was inspected 
to see if the adults had emerged. The result was as follows when the insects 
were removed on 23. vii. 18: 
Pigmentation 
(a) Black box (kept, in partial darkness) contained 8 (3^, 5 b.) 
11 (3<?,4$,4L.) 
1 (<*) 
moults 
and 
(b) White box (kept in complete darkness) contained 34 (5^, 14 9 , 15 L.) O to OO 
N.B. Expt. YII a was vitiated by the entrance of light. It was intended 
that it should be carried out in complete darkness. Owing to the dry atmosphere 
in the thermostat, a minute pin-point crack developed in the lid of the outer 
wooden box, and light entered in sufficient amount to affect a small central 
area on photographic paper placed in the bottom of the box. 
Experiment VIII (rate at which lice darken on black). 
Second and third stage larvae that had been raised from the egg in a white 
box on white flannel and which were consequently pale or but slightly pig¬ 
mented, were transferred on 25. vii. 18 to a black box containing black cloth. 
After 36-48 hours had elapsed, 5 adults had emerged and they were dark or 
moderately pigmented. On the day following some more dark adults and 
dark third stage larvae were found in the black box. Diffuse light entered 
the box whilst it was in the thermostat. 
Experiment IX (black and white. Lice in absolute darkness). 
On 29. vii. 18, seven pale third stage larvae were placed on black cloth in 
a black pill-box enclosed in a black wooden box as in Expt. VII, it being first 
ascertained that the latter was light tight. As an extra precaution, these 
boxes were enveloped in black cloth and the bundle placed in a third box. 
The lice were fed twice daily in a photographic dark room and were kept at 
31° C. during the intervals between feeds. The insects were maintained inside 
the triple boxes except when being fed in the dark room through the gauze 
top of the innermost box. 
The adults emerged on 30. vii. and all of them from the black as well as 
the white box were pale. 
Experiment X (black and white. Lice in a bright light). 
A number of first stage larvae were placed in two vertical glass tubes each 
plugged below by a cork upon which was spanned in the one case white linen 
in the other black sateen. They were exposed to bright light day and night 
for about two weeks. (The experiment ran concurrently with Expt. II as 
