328 ZOOLOGY. 
cuneiform, staff-like bodies, with very finely-pointed ex- 
tremities (primitive nerve-fibres?), which are surrounded 
by loosely aggregated ganglionic globules.’’ (Siebold’s 
Anatomy of the Invertebrates, ) 
In walking, the locust, beetle, or, in fact, any insect, 
raises and puts down its six legs alternately, as may be 
seen by observing the movements 
of a beetle (Fig. 287). While the 
structure of the limb of a ver- 
tebrate and insect is not homol- 
ogous, yet the mechanism or 
functions of the parts are in 
the main the same, as indicated 
in Figs. 288 and 289. 
The footprints of insects are 
sometimes left in fine wet sand 
on the banks of streams or by 
the seaside. 
In Fig. 290 the black dots 
are made by the fore, the clear 
circle by the middle, and the 
black dashes by the hind legs 
(Graber). 
The wings are developed as 
folds of the integument, and 
strengthened by hollow rods 
called ‘‘ veins ;’’ their branches 
Fig. 288,—Section of the fore leg of called ‘‘ venures.’’ There are 
a Stag beetle, showing the muscles. S. 
extensor, B, flexor of the leg; s, ex- in the wings of most insects 
tensor ; 0, flexor of the fe: +0, fe ; G om 3 . 
ue tibia: 7, tarsus; &, claw, 1092.6, SiX Main veins—i.e., the costal, 
een enth cuiniwed.AtterGrater the subcostal, median, subme- 
dian, internal, and anal. They 
are hollow and usually contain an air-tube, and a nerve 
often accompanies the trachea in the principal veins. The 
arterial blood from the heart (as seen in the cockroach by 
Moseley) flows directly into the costal, subcostal, median, 
and submedian veins ; here it is in part aérated, and returns 
to the heart from the hinder edge of the wings through the 
hinder smaller branches and the main trunks of the internal 
