THE ANT HO ZO A 



65 



from which it will be seen that the theca appears to cut the 

 mesenteries in two. It will also be noticed that, in an aporose 

 coral such as is shown in Fig. XXX. 2 and 4, the only com- 

 munication between the cavities in the edge-zone and the remainder 

 of the intermesenterial spaces is by way of the lip of the calicle, 



Fig. XXX. 



1. — Astroiiles calicularis. Sclieiiiatic longitudinal section thnnigh a zooiil and a bud, show- 

 ing the relations of the soft tissues to the corallum. In tliis, and in ligures 2 and 4, the 

 thick black line represents the soft tissues, the corallum is gray. The sections are much 

 siniplitied, the mesenteries, etc., being omitted. .S, stomodaeum ; T, tentacles ; C, coenosarc ; 

 Col, columella. 



2. — A similar section through a single zooid and bud of .^tylophora digitatn. On the left 

 of the figui'e the coenosarc is seen to be .supported on echinulations of the coenenchyme. 



3. — A diagram illustrating the process of asexual reproduction by unequal division. 



4. — Schematic longitudinal section through three coralities of I.ophohdia proli/era. In the 

 upper part of the ligure the larger zooid is seen to be in connection with the .smaller zooid 

 formed from it by division both internally and externally by way of the edge-zone. The lowest 

 zooid ha.s lost all organic connection with the other members. P, edge-zone ; other letters as in 1. 



5. — A section through a dividing calicle of Mussa, showing the union of two septa in 

 the plane of division and the origin of new septa at right angles to them. 



t). — Side view of the upper part of the specimen shown in 5. (4 original, the rest after 

 G. von Kocli.) 



but in the perforate coral the theca is permeated by numerous 

 anastomosing canals lined by endoderm, which place the cavities 

 of the edge-zone in communication with the central coelenteron. 



According as these canals are absent or present, the Sclerac- 

 tiniae are classified as Aporosa or Perforata, and the anatomical 

 character in question is sufficiently definite to afford a basis of 

 classification. There are, however, some corals which cannot be 

 placed in either of these groups. 



