512 



CCELENTERA TES. 



common trunk. The foot swells out like an onion and becomes transparent, 

 curves, and sinks into the stand ; and the stock, which during its period of 

 inactivity lay prone on the ground, assumes an erect position. In these sea-pens 



an alcyonarian coral, Alcyonium (nat. size). 



the parts of the stock may be compared with the parts of a feather, the whole 

 being bilaterally symmetrical, and the single polyps being carried on the leaf-like 

 lateral appendages of the stem. The sexual animals, which are provided with all 

 the organs necessary for a polyp, take in the food and reproduce themselves. The 

 other less perfect brethren, called zooids, although more or less resembling these, 



