148 
Purported New Species , etc. 
sumably pure breeds of capitis and corporis respectively, the form of the head 
varies so that its taxonomic value is largely vitiated. In cross breeds a com¬ 
plete series of intermediate forms may be observed. 
Antennae. The statement that capitis has shorter antennae than corporis 
likewise holds for typical forms. In presumably pure breeds, a distinct varia¬ 
bility is however noticeable, and in cross breeds all kinds of intermediate forms 
of antennae are seen. In pediculi derived from apes and monkeys, the antennae, 
like the head, are of the capitis type. 
In body-lice from negroes (“P. nigritarum Fabricius”) Fahrenholz de¬ 
scribes the antenna as inverted-pear-shaped, the author apparently meaning 
to refer to the form of the segments composing the antenna, but his wording 
implies that the whole antenna has this form, this being absurd. He only 
describes the form from a single $ which may well have been a capitis with 
collapsed antennae. 
Thorax. It is difficult to define the shape of the thorax dorsally because 
the outer margin is virtually colourless and the pigmented portions which lie 
within the margin mislead the eye into accepting them as indicating the form 
of the thorax. Its shape varies slightly in individual specimens, the lateral 
contours being more or less convex. 
Therefore, when Fahrenholz describes the shape of the thorax in “P. 
capitis angustus ” as ‘‘parallel sided,” in dealing especially with balsam-mounted 
specimens, the supposed character must be dismissed as valueless. The six large 
hairs situate dorsally on the thorax in all pediculi I have examined, are stated 
to be absent in “P. lobatus ” but I firmly believe that they were merely over¬ 
looked by being viewed through balsam (see further under Pigmentation). 
Abdomen. Fahrenholz, writing of the <$ abdominal structures, refers to 
what we have termed the dorsal bands, genital plate, and anterior ventral 
band. His statements regarding these structures are largely controverted 
in the following section on Pigmentation, q.v. 
The Genital plate , in the <£, is stated by Fahrenholz to be bipartite in 
“P. lobatus ” and “P. capitis maculatus/' and absent in other pediculi. We 
have, however, shown that this structure varies in normal individuals of one 
lot (see Keilin and Nuttall, Parasitology , xi. 282, fig. 3) and consequently there 
is no significance to be attached to its consisting of one or two parts, whilst 
it is never absent. 
In the <j>, the posterior abdominal lobes , when retracted, become approxi¬ 
mated, giving the semblance of a slit in contrast to the usual bilobed appear¬ 
ance of the end of the abdomen when the lobes are protruded. This accounts 
for what Fahrenholz gives as a specific character in “P. lobatus .” 
The gonopods, in the 9, are stated by Fahrenholz to point back in “P. 
friedenthali, ” inward in “ P. assimilis ,” and to be “short ” in both forms, being 
intermediate in shape between those of capitis and corporis. I find, however, 
as already stated elsewhere (Nuttall, Parasitology, xi. p. 341), that the form 
of the gonopods is inconstant in both of these races of P. humanus and that 
