Physiology of Ilgematopinus tenuirostris, Barm. 85 



epidermis. The legs also show many thickenings of the 

 epidermis, especially in their last two joints. All the* 

 thickenings have a dark brown colour. The structure of the 

 epidermis is most peculiar on the antenna;. In general the 

 integument here shows no divisions ; but it appears somewhat 

 lighter, which indicates a less firm consistence. But each 

 joint of the antennae is furnished with two or more chitinous 

 plates. These are thick, firm, and placed parallel to the long 

 axis of the antenna. Their form is different in the different 

 joints. "The first and second joints have bacilliform, and the 

 third uncinate plates ; the plates of each pair are always 

 united by a somewhat darker chitinous layer (tig. 7). In 

 .the fourth and fifth joints the structures in question are parti- 

 cularly noteworthy. In the fourth joint we find two uncinate 

 plates, one of which, however, is surrounded (fig. 7 c) by a 

 lighter chitinous pad. The latter, in turn, shows a small 

 circular excentrically placed opening. Below the pad there is 

 another almost rectangular thickening of the oute;* chitinous 



of 



layfer. The fifth joint has a similar armature symmetrically 

 placed. Here there is, on one side only, a triangular plate ; 

 and at the same level with this on the other side there lies 

 a quadrangular chitinous plate, and beneath this a rounded 

 slightly bordered chitinous piece (tig. 7 d), showing a small 

 rounded opening near its middle. What purpose these open- 

 ings serve, whether they lead to the organs of hearing or c 

 smell, could not be ascertained. This, however, is certain 

 they are connected with the nervous system, as is shown by 

 the course of the two nervous filaments which I was able to 

 trace distinctly to the end of the fifth joint. 



Beneath the epidermis lies the cutis, a somewhat darker 

 structureless layer of about the same thickness as the epider- 

 mis, as is distinctly shown by transverse sections and the 

 abdominal processes of the female. 



The hairs have still to be mentioned as special structures 

 of the integument. As already stated, these vary considerably 

 in length* They are all of a pale yellow colour, present ex- 

 actly the same structure, and, like the hairs of the Arthropoda 

 generally, are homogeneous. In the interior they have a 

 cavity which is produced in the form of a tube through epi- 

 dermis and cutis, and thus connects them with the body-cavity 

 and the nutritive organs. 



Quite different from these hairs are the structures which 

 arise from the terminal surface of the fifth joint of the 

 antennae. These constitute small round-ended bacilli, without 

 any recognizable internal cavity or special structure. I count 

 five upon each antenna (tig. 7 b). I could not hesitate a moment 



