THE COELENTERATES AND CTENOPHORES 



97 



of the solitary forms are the sea anemones and of the colonial 

 forms are the corals, gorgonians, sea pens, and sea pansies. 



Fig. 55. — Section of a young sea anemone, ss, sagittal plane; tt, transverse 

 axis; I, II, III, septa of first, second and third orders; ek, ectoderm; en, ento- 

 derm; /, mesenterial filament; m, muscle; r, directive septa. {After Boveri, from 

 Hertwig's Manual by Kingsley, courtesy of Henry Holt and Co.). 



Fig. 56. — Transverse section of Zoantharian. AB, plane of symmetry; x, 

 siphonoglyphe. {From Hertwig's Manital by Kingsley, courtesy of Henry 

 Holt and Co.). 



Anthozoa occur in greatest abundance in tropical seas where their 

 skeletal remains build massive coral reefs. 



