308 
Studies on Pediculus 
length from the base of the penis to where the duct became muscular. 
The whole course of the duct is best shown in Text-fig. 4, but its position 
is also shown in Plate III, figs. 1, 2, D. ej. It is evident from what 
has been said that when the vesica is everted the duct follows the penis. 
Fig. 4. Pediculus humanus Dissection of the retracted copulatory apparatus. The 
basal plate is cut across and the muscles running from its base to their insertions in 
the vesica, etc., are stretched. Figure slightly schematized. 
traversing the vesica, where it runs parallel with the fibres of the re¬ 
tractor muscles which stretch outward in the cavity of the sack. The 
protrusive movement of the basal plate and whole copulatory apparatus, 
as is seen from sections, also entails a corresponding movement of the 
accessory glands which lie partly dorsal to the plate. 
