. an 
ASCIDTA. 87 
Fig. 4 is a Botryllid colony (Botryllus). 
Fig. 5 shows the union of two Ascidiozooids, in a Com- 
pound Ascidian colony, to form a common 
cloaca (c.c.) in the common test. 
Figs. 6 to 8 show the three forms of body found amongst 
the Ascidiozooids of Compound Ascidians. 
Fig. 6 is from a Botryllid colony. 
Fig. 7 is from a Distomid colony. 
Fig. 8 is from a Polyclinid colony (all from right side, 
magnified). 
Fig. 9. Section through outer part of test of Asczdia to 
show ‘“‘vessels’’ and “‘ bladder”’ cells. x 50. 
Fig. 10. Diagram of Ascidia to show the arrangement 
of the blood system, from left side, in correct 
morphological position for comparison with 
Vertebrates. 
Puate LV. 
Fig. 1. Part of branchial sac of Ascidia mentula, from 
the outside. x 50. 
Fig. 2. Part of branchial sac of Ascidia mentula from 
the inside. x 50. 
Fig. 3. Small part of last. x 300. 
Fig. 4. Part of the dorsal lamina. x 40. 
Fig. 5. Transverse section of the endostyle. x 200. 
Fig. 6. Blood corpuscles of Ascidia. 
Fig. 7. Part of section of wall of intestine showing 
refringent organ, spermatic tubules, &c. 
Fig. 8. Ocellus from the branchial aperture, in section. 
The heart and pericardium, in side view. 
ce 
ue 
do 
Fig. 10. The heart and pericardium, in section. 
Bee ft = Group of renal vesicles: - x 50. 
Fig. 12. Part of a renal vesicle, more highly magnified. 
Fig. 13. Two cells from wall of renal vesicle, 
