HISTOLOGY OF THE LOCUST AND CRICKET. 
187 
they always run nearly perpendicular to the surface to the cuticula. 
Directly over each pore there sits a stiff chitinous tapering hair (Fig. 4 h 
and h 1 ), which is generally slightly curved. This relation of the hairs 
and pores has also been described by Leydig, 227 and is well known to 
naturalists. The hairs are all small, though very unequal in size, the 
difference in the extremes being much greater than between h and h 1 in 
Fig. 4. The hairs do not stand upright, but are so inclined as to point 
towards the posterior end of the body. 
Each hair is constricted around its base (Fig. 03 /(), forming a narrow 
neck, below which it expands again, spreading out to make the circular 
covering membrane of the hair pore. This membrane is very thin, but 
has a thickened rim. In consequence, of this constriction these hairs 
are commonly said to be articulated. They are not homogeneous, 
but have a distinct medulla (Fig. 63 h), which is probably a prolonga- 
tion of the cell which forms the hair. These cells have been described 
by Graber. 228 They were formerly called " Haut(lriiscn v by Leydig and 
others. They are, as it were, suspended from the inner side of the large 
pores as the hairs are from the outer. They are somewhat pear-shaped, 
and four or five times the diameter of the ordinary epidermal cells, and 
have correspondingly large round nuclei ; their contents are very gran- 
ular. There are usually two or three, rarely but one nucleus in each 
hair-cell. Graber suggests the name of trichogens for these cells. They 
are probably strictly homogeneous with the scale-cells of the Lepidop- 
tera ; the cells differ in the two orders of insects in that they bear a 
round hair in one case, a flattened hair in the other. The plausibility 
of this suggestion must, I think, strike every one who is acquainted 
with the account of the structure and development of the scales in but- 
terflies given by Semper. 229 If the homology is correct, these hair or scale 
cells must be regarded as specially characteristic of insects, or, possibly, 
of arthropods generally. 
The articular membrane, though a part of the cuticula, has either no, or 
at most very few, hairs. In the locusts the cuticula at the joint is much 
thicker and paler in color than elsewhere (Fig. 5, art.), being not only 
thrown up into folds, but also covered with numerous minute pyramidal 
spines. In the locust the first abdominal segment lacks an independent 
articular membrane, its own entering into the formation of the sterno- 
coxal membrane, or articular capsule of the third or metathoracic limb. 
On the sides of the segment a kidney -shaped piece of the cuticula un- 
dergoes peculiar modifications to enter into the formation of the tym- 
panal apparatus. 
In Anabrus the cuticula presents the following characteristics, besides 
those which have been mentioned as found in both it and the locusts: 
First, there are projecting conical nodules scattered irregularly over 
it, as can be seen in a surface view. (Fig. 59, b b.) These cones are less 
m Leydig: Lehrbuch der Histologic, 1857, p. Ill, Fig. 56. 
™ Graber : Denk. Wien. Akad., xxxvi, p. 35 (1876). 
m Semper : Zeit. fur wiss. Zool. Bd. viii, p. 328. 
