ZooL.— Vol. III.] BANCROFT— COMPOUND ASCIDIANS. 



171 



the ampullae of the opposing colonies until they come in 

 contact with one of its blood-vessels. Then the walls of 

 the ampullcE and the vessel fuse, their lumina become con- 

 tinuous, and the common vascular system is established. 

 Several stages in this process are shown in text-figs, i to 3. 



Tbxt-Fig. I. 



Fig. I. Two erabryozooids of Family II that have fused, from below, a., ampullae; 

 b., bud; end., endostyle; li., heart; x x, the pedicels of two ampullfe of the left hand 

 zooid that have fused with the vessels of the right hand zooid; the arrows indicate the 

 places where blood was seen to enter the zooids from the vessels in the test. Drawn 

 with the camera; x 43. 



Text-Fig. 2. 



Fig. 2. The ampullae and connected vessels of two colonies that are undergoing 

 fusion. The ampullae of one colony are lettered, and those of the other are numbered. 

 Camera; x 43. 



(4) January 20, 1903. 



