142 
Biology of Pediculus humanus 
or unfertilized, and the number laid in either case is equally influenced 
bv the conditions of temperature and nutrition affecting the female. 
4. Lice that are confined continuously on the body do not gorge 
as they do when fed at longer intervals; by partaking of frequent 
small meals of blood they will doubtless assimilate their food better 
and this may account for their laying more eggs. 
5. It may be mentioned incidentally that there is no evidence of 
the occurrence of parthenogenesis in lice. Unfertilized eggs, in my 
experience, invariably shrivel up soon after they are laid. 
6. The process of oviposition in P. lmmanus is described for the 
first time in this paper. (This is extraordinary considering the length 
of time the insect has been kpown to man!) It is shown that the gono- 
pods, whose function has not hitherto been known, serve to clasp 
human hair upon which the insect oviposits; without these organs 
she could not lay eggs on hair in proper alignment, such alignment 
being an important safeguard in preventing injury to the eggs and 
thus maintaining the species in nature; the gonopods constitute a 
special adaptation to a phase of its parasitic life. 
The egg, whilst in the ovary, has its operculum directed toward 
the head of the female; it issues from the vagina with its pointed 
end first. The egg is asymmetric, its ventral contour, seen in profile, 
being flattened. The ventral surface of the egg glides out upon the 
ventral wall of the vagina and thence upon the hair or other support 
upon which the insect oviposits. To bring the gonopods into play, 
the female walks backward along the hair, flexing the gonopods upon 
it; the latter then slide down about the hair to whose dimensions 
they are closely adapted. The expulsion of the egg follows a few 
« moments after the gonopods have clasped the hair; the expulsion 
taking place in the fraction of a second, after which the female 
promptly walks forward, away from the egg, releases the hair from 
the grip of the gonopods, and seeks a place of rest. The gonopods 
facilitate the deposition of eggs on filamentous fabrics, but neces¬ 
sarily function imperfectly on fabrics, being primarily organs for 
the performance of oviposition on human hair. The cement, which 
attaches the hair to its support, issues before the anterior broad portion of 
the egg has emerged, and, flowing about its posterior end and the hair, or 
fabric, hardens rapidly. The cement behaves like chitin in its resistance 
to the effects of chemical agents, the latter destroy the hair or fabric 
before affecting the chitinous eggshell and its cement. The orientation 
of the egg upon the hair or substratum is such that the young louse 
