Page:Natural History, Mollusca.djvu/328

From Wikisource
Jump to navigation Jump to search
This page has been validated.
316
TUNICATA.—CLAVELINADÆ.

system of organs for respiration, circulation, and digestion.

PEROPHORA.

The rows of oval rings are the cells of the branchial sac, and the arrows show the course of the blood as it circulates from the oblong heart at the bottom of the body all around the system.