PLATE XIII. 
Colella thomsoni, n. sp. 
b.c. Blood-corpuscle. 
br.s. Branchial sac. 
ec. Ectoderm. 
en. Endostyle. 
gm, gm'. Buds. 
h.gl. Glandular tubules on intestine. 
i. Intestine. 
0. Ovary. 
ce. (Esophagus. 
ov. Ova. 
p-hr. Peribranchial cavity. 
r. Kectum. 
st. Stomach. 
t. Test. 
t.v. Spermatic vesicles. 
V. Vessel in test. 
Fig. 1. Part of a transverse section through the peduncle, showing the system of rami- 
fied vessels ; magnified (S., 1 inch). 
Fig. 2. A small part of another section; magnified (S., 1 inch). 
Fig. 3. A small part of another section ; magnified (S., 1 inch). 
Fig. 4. Part of another section ; highly magnified (S., \ inch). 
Fig. 5. Part of the wall of one of the vessels from the peduncle ; more highly magnified 
(S., inch). 
Fig. 6. Some of the ectoderm cells from a vessel ; still more highly magnified (Z., j3^). 
Fig. 7. Part of a section, from the upper part of the peduncle, showing young buds ; 
magnified (S., 1 inch). 
Fig. 8. Part of a section from still further up the peduncle, showing more advanced buds 
still connected with the vessels ; magnified (S., 1 inch). 
Fig. 9. The end of a diverticulum, from one of the vessels of the test, showing the 
commencement of the formation of a bud ; highly magnified (S., i inch). 
Fig. 10. Longitudinal section of a very advanced bud or young Ascidiozooid (1 mm. in 
length), showing all the important organs of the body highly magnified 
(S., ^ inch). 
