16 OCEAN LIFE. 



cortex consists of the layer of Polypes, with a variable propor- 

 tion of calcareous matter, secreted within their texture ; it is at 

 times, like paper in thinness, and in other species, is thick and 

 spongy." In the Gorgonia verrucosa, Cavolini states that the ova, 

 which are developed in an ovarium, situated at the base of each 

 polype, doubtless in the meso-gastric folds, are discharged by 

 eight small pores, situated at the bases of the eight tentacles. 

 The ova escape as ciliated 'planulcB* (planus flat, applied to 

 flat ciliated forms of larva,) of an ovoid form, which emerge 

 from the ovarian pores with their small end foremost. In the 

 month of June, a Gorgonia, six inches in height, discharged 

 ninety such larva in the space of an hour. They first rose spi- 

 rally towards the surface of the water, then swam horizontally. 

 They have the same property as the ciliated planulse of the 

 marine -Hydrozoa, of changing their form, by the contraction of 

 their tissue, a property which the ciliated zoopores of sponges 

 and algae do not possess. When the larva of the Gorgonia 

 rested, they attached themselves to the sides of the vessel, con- 

 taining them, by their larger end. The hues of Gorgonidae are 

 gorgeous and varied. The brightest red, crimson, purple, orange, 

 and yellow are common, besides white, brown, and black, and the 

 polypes add other and more delicate tints, when their star-like 

 flowers are in full blossom. 



PENNATULID^E. 



SUB-ORDER Alcyonaria, unattached, either free, or with their 

 base burned. These zoophytes are either flat plates, simple 

 stems, or plume-like fronds. The polypes occur on one or both 

 sides of the stem or branches, and, in a single genus, (Umbel- 

 lularia) form a cluster at the extremity. The base of the zoo- 

 phyte is oftvn somewhat enlarged, and some species, by means 

 of it, are planted in the mud. The greater part of them secrete 

 a slender, solid axis, along the main stem or mid-rib of the frond, 



