Tue Hog Louss 703 
line with their basal articulations. Here the chitinous structure is no 
longer a canal, but two divergent arms which may correspond to the 
statumen penis of Nuttall. 
When killing lice with chloroform it was noticed that the males frequently 
ejected the copulatory apparatus in part or completely, and this character- 
istic has been utilized in the study of the musculature and movements 
of the apparatus. The protractor muscles of the basal plate have their 
origin in the ventral wall of the ninth abdominal segment where it turns 
dorsad, and their insertion in the anterior ventral surface of the basal 
plate. They form a thin plate of muscle fibers lying parallel to one another 
and identical in outline with the plate. When they contract, the basal 
plate is drawn caudad until the proximal edge lies just anterior to the 
boundary between segments 6 and 7, and the parameres are protruded 
from the sexual orifice for from one-third to one-half their length. Their 
dorsal aspect shows no collar-like membrane forming a sheath for the 
transit of the vesica penis as figured by Nuttall in Pediculus. Its place 
is taken by the already described upgrowth of the basal plate. They point 
dorsad and slightly cephalad, so that their ventral aspect is now caudad 
(Plate LXIV, 4). They are controlled by muscles which lie at rest along- 
side them and which, by their contraction along with or immediately 
following that of the muscles of the basal plate, hold them rigid during 
copulation. There are ten muscle strands on either side, of which the 
five posterior lie in a regular succession and the five anterior in a close 
group. They originate in the ventral body wall in the region of segments 
6, 7, and 8. The posterior strands are inserted in the deep lateral fold 
of the upgrown ventral lamella of the basal plate (Plate LXIV, 5), and 
the anterior strands are inserted as a stout tendon in the anterior dorsal 
border of this upgrowth. Myjéberg (1910:189) has explained the purpose 
of the genital plate, at any rate in some cases, as the basis of attachment 
of these muscles, and his figure of Haematopinus bufali de Geer shows 
them inserted in the border of the genital plate. Cross sections through 
this region in the hog louse show these muscles originating laterad of the 
genital plate. The dorso-ventral lateral muscles of the abdomen next 
contract and drive the coelomic fluid caudad and into the vesica penis, 
which is thereby everted carrying the ejaculatory duct and the penis 
along with it. The thick muscular part of the duct has been drawn 
caudad until its posterior end lics at the level of the articulation of the 
