G. H. F. Nuttall 
151 
(Grade 6) down to practically colourlessness (Grade 0) was painted on paper 
with water-colours, and the various degrees of pigmentation exhibited by 
the lice were recorded on a chart with the aid of the colour scale. The speci¬ 
mens were at first charted in no particular order, but afterwards they were 
ordered in accordance with the degree of pigmentation shown by their genital 
plates. The results of this colorimetric study are shown in the accompanying 
Chart II wherein the thickest line among the curves records the gradual fall 
in the degree of pigmentation shown by the genital plate in 20 do • It will be 
noticed at once that the degree of colouration of the genital plate bears no 
relation to that of the other structures. This plate may even be colourless 
whilst all the other structures are distinctly pigmented. The degree of pig¬ 
mentation appears fairly uniform in the pleurae, whilst in some other structures 
(i.e. frons, sides of thorax, etc.) it often rises and falls, sometimes synchronizing 
with the varying colouration of other parts and sometimes not. In short, 
there is often agreement but no constant relation between the degrees of 
pigmentation shown by the different parts. 
These observations bear on my criticism of Fahrenholz’s work in so far as 
they prove that considerable individual variation may occur in the degree of 
pigmentation shown by different parts of the exoskeleton of Pediculus and 
that this has to be taken into account in all descriptions. 
III. 
SUPPLEMENTARY NOTE UPON THE SYNONYMY OF PEDICULUS 
HUMANUS. 
The following synonymy requires to be added to that supplied in my 
previous paper in Parasitology , xi. pp. 334-7: 
(a) Pediculus humanus race corjporis. 
1805. Pediculus nigritarum Fabricius 1805, p. 340. From negroes. 
1816. Pediculus albidior Olfers 1816, p. 81, cited by Fahrenholz, vu. 1916, 
p. 270. 
1816. Pediculus nigrescens Olfers 1816 {fide Fahrenholz, loc. cit.). 
1910. Pediculus capitis vestimenti Neumann 1910, p. 412. “II me parait 
logique de conclure qu’il conviendrait de faire descendre P. vesti¬ 
menti du rang d’espece a celui de sous-espece et de le considerer 
comme P. capitis vestimenti This procedure is not permissible 
under the rules of zoological nomenclature, for humanus has priority 
over capitis as a specific name and corporis has prioritv over vesti¬ 
menti as a sub-specific varietal, or racial name. 
1915. Pediculus corporis var. nigritarum (Fabricius 1805) Fahrenholz 1915, 
p. 597, fig. 1. 
1916. Pediculus humanus chinensis Fahrenholz x. 1916, p. 87. From Chinese. 
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