1 12 Introduction to Animal Morphology. 



colony there is ofteu an ecderonic tubular or laminar con- 

 necting material (peritheca), often as horizontal plates uniting 

 the zooids (cpithecal dissepiments). 7. A central columella may 

 form in the middle of each calyx, corresponding to the 

 enderon forming the floor of the somatic cavity below the 

 stomach ;' when this is a distinct pillar it is called columella 

 propria ; when it consists of the centrally united septa, it is 

 c. septalisw pseudocolumdla. 8. Smaller detached rods around 

 the columella, formed of the dismemberments of septa (pah" 

 or bacilli}. 9. Short transverse bars may unite one septum to 

 its neighbours (synapticula). 10. Horizontal plates growing- 

 inwards from the sides of the septa (endothecal dissepiments} 

 may divide the chambers into storeys ; when these are com- 

 plete tlu-v an- called tabuhr. A central pillar-like elevation of 

 the tabulae is a columella parietalis. The presence of a coral- 

 lum prrclutlt-s locomotion. 



The stomach wall often contains pigment (hepatic) 

 cells. The somatic cavity extends as a canal system 

 into the ccenenchyma ; within it chyle corpuscles cir- 

 culate in a vehicle of sea water, which enters by the 

 mouth, and is expelled through the pores at the tips 

 or sides of the tentacles. On the mesenteries are 

 richly ciliated coiled threads (craspeda) containing 

 guanin, and consisting of an axis, often a central 

 closed canal, and a peripheric layer armed with thread 

 cells : these may protrude through small openings 

 (cinclides) ; sometimes found in rows on the body 

 wall, through which sometimes the chylaqueous fluid 

 escapes from the body cavity. 



Reproduction is sexual, the sexes being separate 

 or united. The ova and spermatozoa arise along the 

 borders of the mesenteric folds, and when immature 

 the sexes can only be distinguished by the microscope. 

 The ova are fertilized in the body cavity, and the 

 ciliated planuliform larvae are expelled by the mouth. 



