Stndiei^ on Pedicidus 
;31<i 
treated with caustic potash and mounted in balsam, it therefore only 
shows the chitinous structures. 
Text-fig. 6 illustrates certain muscles that may or may not play a 
part in copulation; retractor muscles running from the posterior dorsal 
and ventral surfaces of the vagina {M. retr. d. v. and M. retr. v. v.) and 
running forward to their origin in the intersegmental fold bounding 
the seventh segment anteriorly. The retractor muscles of the uterus 
{M. retr. ut.) may also be noted, these also originate in the above- 
mentioned intersegmental fold and are more numerous than shown in 
the section, for they are mostly situated laterally to the median line. 
All of these muscles doubtless play an important part, together with 
the constrictors of the uterus, in the expulsion of the eggs. The function 
of the fine, backwardly directed chitinous teeth protruding from the 
fi 
Fi^^. !l. Pc<li< uln.'i liinnanus J. Posterior aspect of a female killed whilst in copula and 
fixed, the male having subsequently been pulled away. Sketch. 
vaginal wall is probably in the main to aid in the expulsion of the eggs, 
it is difficult to see how they could assist materially in copulation. 
In Text-fig. 9 a sketch is given of the posterior aspect of a female 
which was killed and fixed whilst in copula, the male being subsequently 
pulled away. The vagina is seen to have been fully dilated by the 
male copulatory apparatus; the parts are lettered in accordance with 
the figures previously described. 
THE ACT OP COPULATION. 
Historical. 
The first author to give any information about the process of copula¬ 
tion in P. humanus is Warburton (1910, pp. 23-27), who states that he 
observed a female copulating on the fifth day after ecdysis, after which 
copulation took place frequently and lasted for hours; he considered 
