284 Proceedings of Royal Society of Edinburgh. [sess. 
coelomata will be furnished by ontogeny. The body naturally falls 
into three parts, consisting of (1) the pre-oral epistoine, which is 
greatly elongated laterally, (2) the rest of the lophophore, pro- 
duced laterally into two arms, which have cirrhi or tentacles, and 
(3) the rest of the body (see figs. 4 and 6). These three segments 
can be directly compared to the three arcliimeric segments. Each 
contains a special section of the coelome, the relationships of which 
to each other have been carefully worked out in Crania by Joubin.* 
In this species the protocoele (Canal de la levre , Joubin) does not 
open to the exterior by protocoelic pores, blit has secondarily 
acquired openings into the metacoeles through a peri-oesophageal 
Fig. 4. — Diagrammatic horizontal section through Phoronis, 
Brachiopoda, and Ectoprocta. 
sinus. The mesocoeles ( Canal de cirrhes , Joubin) open together 
into this sinus, and hence into the protocoele. 
In this manner both the protocoele and the mesocoeles no longer 
open to the exterior, but communicate secondarily with the meta- 
coeles, which, on their part, lead to the exterior by the ‘nephridia 5 
or metacoelic pores. A similar arrangement is found in Phoronis , 
and some Ectoprocta. 
Korschelt and Heider, in grouping Brachiopoda , Phoronis , and 
Ectoprocta together under the old term Molluscoida , especially 
emphasise this division of the coelome into the epistome-cavity 
(grosser Arm sinus der Brachiopoden ), the lophophoral cavity ( Ring - 
kanal der Gymnoldmen , kleiner Arm sinus der Brachiopoden ), and 
* Joubin, Arch. Zool., Exper. (2) iv. 
