324 MR. A. Hancock: on the anatomy 



are tlae means of communication between these blood-cliannels 

 and tlie pallial plexus of both sides, and also with the visceral 

 plexus of the left side. Thus the blood-currents in every part of 

 of the organism are brought under the influence of the heart. 

 One of the suspenders, larger than the rest, connected with the 

 ventral branchial channel, opens into a considerable channel or 

 sinus in the mantle in which the nervous ganglion is placed ; 

 and the vessel which carries the blood from the heart to 

 the great branchial channel has also much the character of a sus- 

 pender. 



There can be no doubt whatever of the fact that the branchial 

 suspenders are tubular, and that they carry the blood, as above 

 stated, from the branclnal network to the visceral and pallial 

 plexuses. I have seen in several instances the channels in the 

 suspenders gorged with blood-corpuscles, as well as the channels 

 connected with them in the pallial and visceral plexuses, and the 

 transverse channels of the gill-sac ; and thus by such natural in- 

 jections the fact has been demonstrated over and over again. 

 And, moreover, I have witnessed blood-corpuscles pass through 

 the channels in the suspenders iu young living individuals of 

 Ascidia sordida. 



When the heart acts in the direction of the dorsal extremity, 

 the blood will at once be thrown into the dorsal branchial channel, 

 and will pass by the dorsal trunk of the compound vessel into the 

 test ; all the transverse channels of the branchial sac Mill be filled ; 

 and through the agency of the suspending tubules or vessels the 

 pallial plexuses of both sides of the mantle, as well as the visceral 

 plexus of the left side, will be supplied in all directions ; while that 

 portion of the blood-current that is retained in the vascular reti; 

 culation of the brauchia will be hurried into the great ventral 

 channel, and by this to the ventral extremity of the heart. But 

 before it reaches so far it will be joined by the streams derived 

 from the visceral plexuses of both sides of the body, and in this 

 way with that fj-om the pallial plexus, chiefly, of the right side. 

 The greater portion of the blood from the left side of the mantle 

 will reach the heart by the ventral branchial channel, having been 

 brought hither by the suspenders. The blood thus returned will 

 likewise have commingled with it that which is drained from the 

 vascular system of the test by the ventral trunk of that system. 

 It is thus apparent that the blood which arrives at the heart in 

 this direction is only a partially aerated current. 



When the action of the heart is turned in the opposite direction. 



