Mar., 1904.] 
Clasping Organs in the Pediculidae. 
107 
NOTE ON MORPHOLOGY OF CERTAIN CLASPING 
ORGANS IN THE PEDICULIDAE. 
Herbert Osborn. 
Tlie results of Parasitism in developing special organs for 
adherence possess a prominent Morphological interest since these 
organs exhibit a high degree of specialization which contrasts 
markedly with the degeneration of other sets of organs. The 
Pediculidae present a number of instances of such structures which 
seem not to have been described in detail and the purpose of this 
note is to call attention to some of them. 
In Haematopinus urius there is a protractile disk at the distal 
end of the tibiae, the purpose of which, as suggested in an earlier 
note, being to press against the hair in opposition to the tarsal 
claw and thus assist in the hold upon the hair. In the previous 
description of this stnxcture no attempt was made to explain the 
apparatus or its movements, but it was mentioned that the disk 
played back and forth in a jht-like depression of the tibiae, and 
the examination of balsam mounts of this organ fails to show very 
clearly the basis of movement. There is a large muscle running 
through the tibia and forking near the middle of the tibial joint, 
one part going to the tibial spur, the other passing on to the tarsal 
joint while from the latter a fiber runs to the base of the protrac- 
tile disk. This would seem able to retract the organ and com- 
bined with an elastic frame- work for the protraction would account 
for the movements. I have been entirely unable to discover any 
muscle strands which would seem to act for the protraction and 
believe that this may be provided for in the movements of the 
chitinous wall assisted partiall}' by the flexion of the tarsal joint. 
The figure shows the distribution of the muscle strands as noted 
in the majoritj' of specimens examined. 
In Haematopinus macrocephalus there is a disk-like organ in 
thb same position as in the preceding species, but it differs from 
the protractile disk in urius in having a convex surface, appar- 
ently membranous, and within the bulb of the organ may be seen 
a half dozen strands of muscles, the contraction of which would 
serve to withdraw the surface membrane. The muscle strand 
runs from the base of the tibiae to the cup-like depression of the 
disk, but not having examined this organ m living specimens the 
extent of the protraction, if any, is unknown. The musculature 
of the tibial joint is shown in the accompanying figure. 
In Euhaematopinus abnormis the posterior jrair of legs is very 
greatly modified, so much so that they cannot serve any function 
as ordinar}’ organs of locomotion, but must be adapted purely for 
clasping, the femur and tibia each possessing expanded disks, the 
former upon the anterior part of the femur and so arranged that 
