248 PROFESSOR HUXLEY ON THE ANATOMY 
EXPLANATION OF THE PLATES. 
Plates XXX. and XXXI 
The following letters and figures have the same signification throughout. 
9 
a, the test; a\ its oral; a\ its cloacal fibrillated layer; a 3 , labial processes of the ascidiozooids ; a\ lip or 
so-called sphincter of the cloacal aperture ; a 5 , cells of the embryonic test. 
6, outer tunic, 
c, inner tunic, or intestinal wall. 
d, atrial tunic. 
e, oral aperture. 
ft tentacular membrane ;/ 1 , haemal tentacle. 
g, g i anterior muscles ; (p 9 posterior or atrial muscles. 
h, peripharyngeal ridge. 
I, endostyle. 
y, epipharyngeal folds. 
k, hypopharyngeal band and sinus ; k\ languets ; te, diapharyngeal band. 
/, branchial sac; l*> horizontal branchial bars; / 2 , perpendicular branchial bars; Z 3 , stigmata. 
ra, alimentary canal ; m\ oesophageal aperture ; m 2 , oesophagus ; m 3 , stomach ; m\ intestine. 
w, tubular organ, probably hepatic. 
o 9 anus. 
■ 
p, m id-atrium ; p l , lateral atria; p% atrial aperture. 
r, heart ; r\ sinuses ; r* 3 stolons of the adult ascidiai ium ; r 3 , vascular bands, connecting the branchial 
sac with the parietal sinus ; r 4 , stolons of the embryonic ascidiarium, or tetrazooid. 
$, ovisac; $ l , its duct; s 2 , lining of the ovisac. 
/, testis ; I 1 , vas deferens ; t% spermatozoa. 
u> yelk ; u l , germinal vesicle ; w 2 , germinal spot ; w 3 , contents of the germinal vesicle. 
w, bud j w l , its peduncle. 
x y alimentary or trophic blastema of the nascent bud; a? 1 , its generative blastema; # 2 , its tegumentary 
blastema. 
y, the circular cellular patch, probably a renal organ. 
z, the ganglion ; z l , nerves ; z 2 , the ciliated sac ; z 3 , the tubercle. 
(By elaeoblast. 
erty embryonic endoplasts within the germinal vesicle. 
bly blastoderm. 
cly cloaca. 
i. ii. in. iv. v. Segments of the blastoderm, i. Cyathozooid. n.-v. Ascidiozooids. 
1, 2, 3, 4, isthmuses. 
/3, the mouth of the 
e 
7, cavity of the* cyathozooid. 
dix 
canal 
*L 
