NO. 1302. AMERICAN PARASITIC A RGULIDJ^^WILSON. 689 



The heart lies in the median line of the body, just beneath the skin 

 of the dorsal surface. It is triangular in outline, the base of the tri- 

 angle extending- squarely across the thorax at its junction with the 

 abdomen. The apex of the triangle passes directly into a long c^din- 

 drical aorta, which reaches forward, diminishing gradually in size, to 

 the brain, under which it opens into the coelom. The walls of both 

 heart and aorta are well supplied with striated muscle libers by whose 

 contraction a rythmic pulsation is produced. 



Jurine (1806), Leydig (1850), and Claus (1875), have each describedin 

 some detail the course of the blood Gnvv^wiiimfoliaceus, and the pres- 

 ent author has observed them in the three American species, versi- 

 color, americanus, sind catostond. 



Of these species the course of the blood in versicolor and catostomi 

 corresponds quite closely with that given for foliacem^ but in ameri- 

 canus it is quite ditferent in several details. 



In the former species the heart has six openings; of these two are 

 median and four are paired at the sides (Claus, fig. 37). 



One of the median openings is anterior and passes into and through 

 the aorta and out into the coelom under the brain. The other is pos- 

 tei-ior and opens backward through the ventral part of the base of the 

 triangle into the sinus around the cloaca. 



Of the paired openings the anterior pair are ventral and consist of a 

 diagonal slit on either side just at the base of the aorta. The posterior 

 pair are lateral and open out of the basal angles of the triangle into the 

 broad sinus which follows the edge of the abdomen. These lateral 

 paired openings and the posterior median opening are guarded by 

 valves, but the other three open and close by the simple approxima- 

 tion and separation of the edges of the slits. 



The heart pulsates about once a second and drives the blood out 

 through the aorta. This stream almost immediately divides, portions 

 going to the right and left and bathing the tissues of the head and 

 antenna', and especially the eyes, which are entirely surrounded b}^ a 

 wide sinus. Another portion turns downward into the common base 

 of the proboscis and sting and there separates, a part going forward 

 into the sheath which surrounds the sting and a part backward into 

 the proboscis. 



All these anterior streams turn back on either side to the bases of 

 the anterior maxillipeds. A part enters the maxillipeds themselves, a 

 part keeps on posteriorly, paissing the bases of the swimming legs and 

 sending out currents to each, and the remainder turns out sidewise 

 into the lateral areas of the carapace. Here it percolates through the 

 lacuna% ])etween and around the numerous stomach ramifications, 

 gradually working its way back in broad curves to the two central 

 side streams, which finally enter the heart by the ventral unguarded 

 slits. 



Proc. N. M. vol. xxv— 02 44 



