700 LAURA FLORENCE 
Nuttall (page 304 of reference cited), “ the essential parts of the apparatus 
are: (1) the basal plate, (2) the dilator (parameres), (3) the vesica penis 
[preputial sac], including its rib or strut, statumen penis, embedded in 
its wall, (4) the penis, and (5) the ductus ejaculatorius.”’ In the preceding 
year Cummings (1916:257) had given the following explanation of the 
terminology used in describing the male copulatory apparatus of Siphuncu- 
lata (Anoplura) and Mallophaga: 
In almost all Anoplura and Mallophaga, it is easy to recognise at once the basal plate and 
the parameres. The basal plate — probably double in origin as two longitudinal apodemes 
—is a chitinous lamina usually, if not always, longer than broad, to the posterior lateral 
angles of which are articulated the two chitinous appendages known as parameres. Between 
the parameres is the mesosome, the parts of which are not so readily made out unless a 
specimen be carefully dissected. Fundamentally, the mesosome is a sac — the enlarged 
and extrusible end continuous with the ductus ejaculatorius. This sac — called by Mjoberg 
“the preputial sac ’’ — presents two regions of chitinisation — a distal and a proximal. At 
the distal end is the rod of the penis or virga, with frequently a splint on each side cailed the 
telomere, and one below — the hypomere.* At the proximal end are the endomeres, usually 
strongly chitinised bands or rods, one on each side, supporting the membrane of the sac, of 
which they are only local thickenings. The whole of the genitalia exhibit enormous variety 
in form, and the mesosomatic parts in particular are occasionally so much modified that it 
becomes difficult to recognise their conformation to the general plan just sketched out above. 
For example, in many Philopterids, such as Docophorus, no sacular portion of the apparatus 
is recognisable, and the distal chitinisations lie well back within the proximal, the whole 
forming a solid and compact mesosome. The above terms are, therefore, adopted solely 
for convenience of description. 
* For these terms, first applied to specialised Philopterid forms, see Waterston, Annals of the S. African 
Museum, vol. x, pt. 9, 1914, p. 279. 
In the hog louse the mesodermal reproductive organs of the male (Plate 
LXIV, 1) consist of two pairs of testes, slender vasa deferentia, seminal 
vesicles, and a long ejaculatory duct, and the ectodermal organs (Plate 
LXIV, 1 and 2) of a penis, a vesica penis, a basal plate, and parameres. 
The testes are oblong-ovate with somewhat bluntly rounded ends, 
and the individuals of each pair touch at one end, where each opens into 
its vas deferens, which almost immediately unite to form a single canal. 
The testes lie on the dorsal wall of the mid-intestine between the meta- 
thorax and the posterior border of the fifth abdominal segment. Their 
free ends point respectively cephalad and caudad, and the left pair 
frequently lie a little anterior of the right. The vasa deferentia are long, 
very slender tubes lying coiled upon themselves and then passing back- 
ward to the region of the eighth abdominal segment, where they pass 
into the seminal vesicles just below the rectum. The latter are closely 
apposed to the wall of the mid-intestine and pass directly cephalad to 
