1884. | in the Legs of Certain Hemiptera. 15 
tinct focus could not be obtained, the pulsations seemed to involve 
the muscular fibers, but scraping the integument thin, so as to 
admit more light, showed that this appearance was due to the 
general indistinctness. 
The pulsating organs are also unaffected by the movements of 
the muscles of the legs. On several occasions, when the legs 
were moving back and forth and the muscles all in action, the 
pulsatile organ has been observed beating naturally, wholly unaf- 
fected by their movements. 
Influence upon circulation, etc—In studying the influence of 
these organs on circulation, they were observed with powers of 
the microscope ranging from 187 to 438 diameters. Either of 
these powers is sufficient to bring out the blood corpuscles. 
In the legs of the insects in question there are two blood cur- 
rents, an outgoing current and a returning current. The out- 
going current passes along the inside of the leg, below the pulsa- 
ting organ, and the returning current passes to the outside of the 
leg, above the pulsating organ. As the blood currents flow near 
the pulsatile organ they move faster, and around the organ itself 
there is a whirlpool of motion. Here the corpuscles can be seen 
rolling over and over one another, and striking against the pulsa- 
tile organ, by which blow they are driven whirling along their 
course, 
The beating of these organs in the Nepide is such as to aid 
circulation in both directions ; and of their influence over it there 
is abundant proof. The motion of the pulsating organ is difficult 
to analyze and describe. In an organ beating slowly the motion 
is seen to originate in the posterior end, spread wave-like forwards 
to about the middle of the organ; the anterior end simply rising 
and falling. It may be likened to the motion of a whip-lash, 
resting on the ground, when the stock is given a quick upward 
stroke. It is to be understood that the “ anterior end” means 
the end towards the head of the insect, and the “ posterior end” 
the one opposite, towards the extremity of the leg. The attach- 
ments have no movement of their own, but are set in motion by 
the organ. This motion in the rapidly-beating organ resolves 
-itself into an upward beat of the posterior end almost simultane- 
ous with a downward stroke of the anterior end. Such an ar- 
rangement would aid the circulation of the blood. As the poste- 
rior end beats upward, it would make room for the outgoing cur- 
