THE SUB-KINGDOM CCELENTERATA. 



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Sub-kingdom CGELENTEKATA. 



Animals whose alimentary canal freely communicates 

 with the somatic cavity. 



Substance of the body made up of two foundation 

 membranes, an outer or ectoderm, and an inner or en- 

 doderm, which correspond, in mode of growth, with the 

 primitive layers of the germ. 



No distinct neural and haemal regions. A nervous 

 system absent in most. 



PecuHar urticating organs, or thread-cells, usually 

 present. 



Class I. Hydeozoa. 



Ccelenterata, in which the 

 ■u-all of the digestive sac is not 

 separated from that of the 

 somatic cavity, and the repro- 

 ductive organs are external. 



Class II. ACTINOZOA. 



Calenterata, in which the 

 wall of the digestive sac is 

 separated fi-om that of the 

 somatic cavity hy an interven- 

 ing space, subdivided into 

 chambers by a series of verti- 

 cal partitions, on the faces of 

 which the reproductive organs 

 are developed. 



