G. H. F. Nutt all 
143 
in issuing readily seizes the hair or cloth as it emerges; the ventral 
surface of the larva coincides with the ventral surface of the egg and 
the operculum usually springs open ventrally. 
7. Lice prefer to lay on horizontal than on vertical surfaces of cloth; 
they greatly prefer to lay on the under surface of fabrics resting on or 
near glass; when confined between two approximately horizontal layers 
of fabric, the interspace between these allowing the insects the freest 
movement, they lay about equally well on the upper and under surfaces. 
8. P. humanus (corporis) shows a marked preference for laying 
on felt and rough filamentous fabrics such as wool or flannelette. They 
will, however, lay readily on silk tricot. They can oviposit on the 
smoothest fabrics (sateen, silk, etc.) but on the -whole avoid them 
because they afford an imperfect foothold. 
9. Under experimental conditions, when given a choice between 
cloth and hair, corporis preferred to lay on hair than on cloth, this 
being contrary to the result of Bacot’s experiments; capitis on the other 
hand, in one lot tested, showed a more marked preference for hair. 
The difference observed was only one of degree and it appears premature 
to draw final conclusions either from Bacot’s or my experiments; a 
larger series of experiments upon a number of different strains of 
corporis and capitis should be carried out under the more exact conditions 
laid down in this paper. If such a series of experiments proves that 
there is a constant difference, -which I am inclined to doubt, it does 
not follow that such a difference is specific. 
10. Contrary to Bacot, my experiments reveal no difference 
between corporis and capitis in the mode of oviposition on hair, in so 
far as concerns (a) the alignment of the eggs on hair and ( b) the laying 
of eggs at the intersection of hairs or on several hairs at a time. 
11. The observation of Bacot, that corporis shows a marked 
tendency to oviposit where eggs have been previously laid, is con¬ 
firmed. Experiments with capitis indicate that this tendency is perhaps 
a little less marked than in corporis, but it is inconstant. 
Hatching. 
The time and temperature conditions required eor the 
HATCHING OE THE NITS. 
(a) Corporis. 
There is no evidence that eggs maintained at 22° C. or under are 
capable of hatching. Eggs kept at the following temperatures have 
failed to hatch: 8-10° C. (Hinclle ms.); 10° C., observation period of 
