442 ZOOLOGY 
into the intestine, the first part of which is also covered by 
the same structures (Fig. 254). The intestine makes a shght 
twist round the ovary, and is then continued into the rectum, 
which runs straight along the dorsal wall of the branchial sac 
Fic. 257.—Mouth of the subneural gland and neighbouring parts in Ascidia 
mentula. After Herdman. 
egr. Epibranchial groove. dl. Dorsal lamina. 
pp. Peribranchial groove. sgd. Duct of subneural gland. 
tn. Tentacles, il. Internal longitudinal bars. 
sg. Stigmata, z Peribranchial zone. 
dt. Opening of duct of subneural gland. 
and opens into the atrial cavity. The internal surface of the 
first part of the intestine is much increased by the existence of 
a typhlosole which projects into its lumen. 
The heart is contained in a pericardium situated ventral 
to the oesophagus in the angle between the posterior limit of 
the branchial sac and the stomach (Fig. 254). The peri- 
cardium contains a corpusculated fluid, its cavity is derived 
from the original coelom of the larva. The heart is a cylin- 
drical tube bent into the shape of a V, the angle pointing 
dorsalwards. One arm of the V is continuous with a ventral 
or branchio-cardiac vessel or sinus which runs along the line 
