Studies on Fediculns 
29lj 
the vaginal pouch (Text-fig. 6). The first pair of legs, as in the immature 
stages, do not differ materially in structure from the others. 
The arrangement of the longitudinal intersegmental abdominal 
muscles (Text-fig. 6) differs from that seen in the male. Dorsally there 
are five pairs of these muscles to each segment, but they are only present 
beneath the last three penultimate tergites. Ventrally there are corre¬ 
sponding muscles; three pairs (omitting two pairs of more obliquely 
directed lateral muscles) at the base of the abdomen in continuation of 
the ventral longitudinal muscles of the thorax, and there are five pairs 
of muscles situated posteriorly beneath the fifth and sixth segments. 
To recapitulate, the great difference in the longitudinal abdominal 
musculature observable in the two sexes may be summarized #is follows: 
Dorsal abdominal muscles are Ventral abdominal muscles are 
present under segments present under segments 
In the 2, 3, 4, 5, 6, 7, 8 2 + 3, 4, 5, 6 
In the ? 6, 7, 8 2, 3, 5, 6 
This arrangement of the musculature was first observed by Landois 
(1865) in the female and by Muller (1915) in the male; the enumeration 
of the segments is in accordance with that advanced by Muller. 
The significance of some of the structural differences above 
enumerated will be considered presently. 
fflSTORICAL. 
Regarding the copulatory organs of the male and female. 
TJie male apparatus. 
The first reference in the literature on lice to the male copulatory 
apparatus is that of Leeuwenhoek. In the English edition of his works 
(1807, p. 163) it is stated that he observed some lice in which he found 
what appeared to be a weapon of defence or hollow sting lying in a 
groove whence it was protruded when the insect was roughly handled. 
He conjectured that the “sting” was present in the male only but did 
not reach a final conclusion on this point. Gaulke (1863, p. 315; 
cited by Landois) took the organ for an ovipositor which served for 
laying eggs in the skin, whereas nearly all subsequent writers, including 
Landois (1865, p. 52), refer to this sting-like organ as the penis. Landois 
described it as wedge-shaped and flattened, as consisting of a long basal 
portion and a slightly bent distal portion. The margins are thickened 
and a slit-like gutter runs from the point back into the basal part. 
The organ is protruded through a transverse slit situated dorsally upon 
