ON THE DIPLOCHORDA. 489 
forcibly to the exterior. The action of the pylorus and that 
of the anus could not be performed more methodically and 
efficiently if they had been provided with nerves and sphincter 
muscles. 
Summarily, we may state that— 
Ingestion is effected by ciliary currents. 
The extra-stomial ingestion is effected by the circum-oral 
band, and by the ciliated walls of the vestibule. 
Intra-stomial ingestion is effected by the cilia lining the 
pharynx. 
The water of the ciliary currents is probably returned along 
the lateral grooves of the pharynx, and then by the corners 
of the mouth to the exterior. 
Digestion is intra-cellular in the stomach (digestive areas), 
but may also be inter-cellular—in the stomach, and in the 
intestine also. 
Currents in the stomach and intestine are ciliary. 
The pylorus and anus are worked by the rhythmic con- 
tractility of the surrounding walls. 
ENTEROPNEUSTA AND PTEROBRANCHIA. 
In the last communication of this series! some points in 
the structure of Cephalodiscus dodecalophus were 
dealt with, mainly concerning the central complex of peri- 
cardial sac, glomerulus, heart, and other parts of the blood, 
vascular, and nervous systems. Many of these points have 
since been confirmed by Schepotieff and Harmer,? and the 
general result is to add considerably to the anatomical 
resemblances of this type to the Enteropneusta. There 
still, however, remains the important difference due to an 
absence of metameric segmentation in the pharyngeal clefts 
and the gonads of the Pterobranchia. 
1 ‘Quart. Journ. Mier. Sci.,’ vol. xlvi. 
2 « Siboga-Expeditie,? Monographie xxvi. 
