Gr. H. F. Nuttall 20D 
peans’ clothing: N. 228, Minneapolis, Minn., U.S.A.; N. 38, Liverpool; N. 204, 
Lambeth; N. 212, London; N. 252, Cambridge. 
Pale to medium : N. 259, 261, 222, from East Indians, British Guiana; 
N. 245, from East Indian, Madras; N. 230, from Sudanese, Khartoum; N; 91, 
from negro, Biskra, Algeria; N. 45, from Japanese, Yokohama; N. 234, from 
Budaga tribe, Nilgiris, India. 
Pale to slightly pigmented : N. 270, from Suaheli native, Zanzibar; N. 241, 
from Samper boy, Kasauli, India; N. 232, from Arab, Khartoum, Sudan; 
N. 90, from Arab, Biskra, Algeria. 
Pale : N. 250, from native Indians, Cerro de Pasco, Peru; N. 233, from 
Arab, Khartoum, Sudan; N. 179, from Chinese, Szechuen; N. 40a, from Eskimo, 
Frobisher Bay. 
Note. I am indebted to the following gentlemen for collecting or pro¬ 
curing the specimens mentioned in the foregoing list, relatively few having 
been collected by me personally: Messrs W. Mansfield Aders, G. E. Bodkin, 
A. J. Chalmers, J. W. Cornwall, J. Donovan, L. Dudgeon, Dr Graham, W. H. 
Hamer, F. Harker, C. Gordon Hewitt, F. Johansen, W. A. Lamborn, J. W. S. 
Macfie, J. L. Mitter, A. Owston, R. E. Ribeyro, W. Rose, P. H. Ross, G. G. 
Sampson, Ed. Sergent, W. R. Sheriffs, S. A. Stericker, C. Strickland, G. L. 
Tuck, A. M. D. Turnbull. 
(6) EXPERIMENTS WHEREIN P. HUMANUS WERE RAISED ON BLACK, 
GRAY, WHITE AND COLOURED BACKGROUNDS. 
Doubtless acting on the suggestion contained in Murray’s paper above 
cited, Sikora (v. 1917, p. 172) carried out experiments regarding the influence 
of black, gray, and white backgrounds upon pigmentation in body-lice 
(corporis). In a subsequent paper, Sikora (ix. 1917, pp. 178-179) records 
similar experiments with head-lice (capitis). I have but recently been able 
to consult this author’s papers, which possess considerable interest as throwing- 
further light on the subject. Sikora states that lice maintained on black, 
gray, and white backgrounds become correspondingly coloured, irrespective 
of whether they are kept in darkness or exposed to light. . 
In This connection I have carried out the following experiments in Cam¬ 
bridge : 
On 17. v. 1918, Mr A. Bacot kindly sent me some corporis (N. 265, 4 d, 6 $) 
which had laid some eggs on gray flannel in one of his breeding boxes. The 
specimens were either pale or moderately pigmented. 
Experiment 1 (Black and White). 
As the eggs hatched out (24-30. v. 18) the unfed larvae were placed daily 
in equal numbers in two pill-boxes so that finally each box contained 46 larvae. 
The pill-boxes were arranged as described by me in Parasitology , x. p. 107, 
with the difference that the one (a) was painted black inside with India ink. 
14—2 
