ALCYONIUM. 



125 



Again, the organs, such as muscles, gonads, and gastric 

 filaments, are much more definite. Thirdly, the coelen- 

 teron is not simple but partially divided thus : — 



Ca:LENTERON<^' ^""f'^ ^^""'^ ^^^ digestion. 



^B, Radial cavities — nutritive and 

 vascular, walls form motor 

 (muscles), skeletal (mesen- 

 teries), and reproductive 

 (gonads) organs. 



Lastly, the ectoderm is tucked in to form a gullet. At 

 the same time we may note the absence, as in Hydra, of 

 definite respiratory, excretory and blood-vascular organs. 



IV.— ALCYONIUM. 



Phylum 

 Class - 

 Sub-Class 

 Order - 



CCELENTERATA. 

 SCYPHOZOA. 

 ACTINOZOA. 

 OCTACTINIA. 



^ig- 57. — ALCYONIUM DiGiTATU.vr. {Ad iiat.) 



Gonad. Coenosarcal 

 / Canal. 



Spicules. 



Radial Cavity. 



Body- wall of Polype. 



A, Isolated spicules. B, A tan^rential section through the entire colony showing 



the polypes in cross section. 



Alcyonium digitatum (Dead Man's Fingers) may be taken as a 

 type of the colonial Actt?tozoa. The colony may be fixed at its base to 

 a foreign body and branching like a coral, or it may grow closely 

 adherent to the tube of an annelid or other body. It is found most 



