Circulation in Spiders. 407 
no dark globules occurring as in most others. 
the blood is now distinctly perceptible. The heart, as was long ago pointed 
out, occupies the superior anterior portion of the abdomen, the blood passing in 
laterally at the posterior part; it contracts 63 or 54 times in a minute, the 
muscular apparatus dragging it forwards and compressing it at the same time. 
When it expands some of the blood seems to regurgitate, but the greater mass 
is driven forwards through a small vessel into the cephalothorax. This vessel 
enlarges and presents every appearance of an auxiliary heart, as attached to it 
on each side is a cartilaginous clavicle-shaped body which is fixed anteriorly 
and moved by lateral muscles posteriorly, and which separating and again 
approximating drive forward the fluid. These cartilages are considerably 
separated anteriorly, but the posterior extremity is merely separated by the 
“vessel, and is parallel to its fellow of the opposite side. The vessel in passing 
forward from the thoracic heart? immediately divides, a branch passing to each 
side of the vomeriform process of the skeleton which is found beneath the cen- 
tral thoracic point, and which gives attachment to certain muscles of the coxe ; 
it then reaches to a point about midway to the apex of the cephalothorax and 
divides intoa lash of branches, oneof which joins its fellow of the opposite side 
and runs down the centre of the forehead, its course being marked by a groove on 
the skeleton internally, giving branches to the eyes; another branch goesdown 
the centre of the mandible or rather nearer to its outer side; and one to each of 
the legs, palpus, jaw, &c.: that going to the posterior legs runs nearly directly 
backwards. Intracing it down the leg we findit nearly in the middle line; it 
terminates a little from the claw by opening directly and at right angles into 
the vein which is of much larger size and generally lies on one side of the 
artery in the tarsus, getting under it however at the joints; the vein being 
larger, and subdividing and againjoining, the blood moves in it much slower than 
in the artery and apparently often stagnates until the vis a tergo produced by 
the accumulation behind drivesit on. If analogy be of much importance, this 
settles the physiological discussion relative to an active power in the capillaries, 
none being here at al! distinguishable. The blood from the several parts, viz. 
legs, mandibles, &c. collects in a lateral thoracic vein, the openings being at 
rightangles. This vein then passes into the abdomen atthe sides of the pedicle, 
a curious valvular structure, which J first saw Jast May in Lycosa saccata, being 
placed here; it is fixed in the middle line and has its outward extremity free, 
being of a crescentic form, and past it the current runs, a liltle eddy occuring 
behind it as it recovers its position. The stream then goes directly tothe pul- 
monary sacs and thence returns to the heart. 
In Clubiona the globules are elliptical and very long, with adark speck about 
