391 
twelve hours. A freshly caught vigorous specimen should be 
chosen for examination (of course a male, the females have 
no wings), or one which, whilst in confinement, has had 
plenty of moist food. If specimens of Blatta be kept in a 
glass vessel for several days without food or water, the circu- 
lation will be found very feeble or almost absent. The 
animals’ blood is almost dried up by evaporation, and if a 
few drops of water be given them they will drink it greedily. 
Fig. 2 is a drawing of the hind wing of B. orientalis. N.B. 
—The circulation is also to be seen in the fore wing; but as 
there is more pigment present here, and the wing is thicker, 
the hind wing is more favorable for examination. The broad 
shaded vessels are the main vascular trunks, which are 
deeply pigmented, the transverse smaller vessels which con- 
nect them being nearly colourless. The dark filaments which 
follow the middle line of the main trunks are fine trachea. 
The direction of the blood-current is marked by the small 
arrows. 
C. G. Carus! showed that in the antenne and legs the 
blood-stream always flowed up on the anterior margin and back 
towards the body on the posterior margin. This is easily seen 
to be the case in the long antenne of the male Blatta. 
In the wings, as will be seen from the diagram, this rule 
is followed only in a general manner in Blatta. a, a are the 
main arteries of the wing; but in 6 and e, e, e the blood also 
flows in a peripheral direction. The main veins are e, @, e, e, 
but there are also a, a, a, and the two vessels which lie one on 
each side of 6, which convey blood in a centripetal direction. 
It must not be supposed that the blood is always to be 
seen flowing in these directions. From comparing a number 
of healthy fresh specimens, I believe this to be its ordinary 
course. When a specimen is exhausted, or stasis from some 
cause occurs in one of the principal vessels, or the heart is 
rendered irregular in action from too tight ligatures, the 
course may be considerably changed for awhile. Thus, the 
current in J, e, e and ¢c,¢ may be reversed. Inaanda' I 
have never observed any but an arterial current. The veins 
e, €, €, € communicate with a venous trunk, which may be 
seen to pour blood into the body at the hind margin of the 
wing; but all the blood coming from these veins does not 
thus at once return to the venous sinus ; but the vessels e, e, e 
also open into the venous trunk, and_a large part of the cor- 
puscles may be seen to turn off from the main stream in this 
1 Fernere Untersuchungen iiber Blutlauf in Kerfern. Verhandlungen der 
Kaiserlichen Leopoldinisch Carolinischen Akademie der Naturforscher 7a, 
Bd. 2te Abtheib, Breslau, Bonn, 1830. 
