AMPHIOXUS. 299 
resembles the pharynx Fig. 213.—VIEw oF AMPHIOXUS FROM 
of Ascidia. Its internal 
walls are mostly ciliated. 
The exdostyle extends 
along the median ven- 
tral line, joined by 
peripharyngeal bands to 
a median dorsal ef7- 
branchial groove. The 
lateral walls of the 
pharynx are perforated 
by a great number of 
pharyrigeal clefts which 
run diagonally back- 
wards as long slits. 
These pharyngeal clefts 
are twice as numerous 
as those of the larva, 
each of the latter be- 
coming divided longi- 
tudinally into two by 
a long tongue-bar of the 
pharyngeal wall growing 
downwards from above. 
The same method 
of feeding as in Ascidia 
is adopted. The water 
and food-particles are 
brought into the phar- 
ynx, and the latter are 
entangled in strands of 
mucus which are even- 
tually carried into the 
intestine at the hind 
end. The water is 
driven through the 
pharyngeal clefts into 
the atrium, a spacious 
cavity which, as in 
Ascidia, surrounds the 
pharynx. In Amphioxus, 
THE RicutT SipE. (Ad zat.) 
Metapleural 
Fold. 
‘Branchial 
Caudal Fin. 
