1 1 2 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. septal is ox psetidocoluviella. 8. Smaller detached rods around 

 the columella, formed of the dismemberments of septa' (/a/f 

 or bacilli). 9. Short transverse bars may unite one sep'tum to- 

 its neighbours {synapticulcB). 10. Horizontal plates growing 

 inwards from the sides of the septa {ettdothecal dissepiments) 

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

 plete they are called tabula. A central pillar-like elevation of 

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

 lum precludes locomotion. 



The stomach wall often contains pigment (hepatic) 

 cells. The somatic cavity extends as a canal system 

 into the coenenchyma ; 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. 



