102 ZOOPHYTES. 



temperate zone, and are common upon some portions of our own 

 coast. 



Order Actinoidea. 



101. The Actinoidea are marine zoophytes. All oceans have their 

 species, yet in the torrid zone they more especially abound, and display 

 most variedly their colours and singular forms. 



The soft Actinidse and the Alcyonaria have the vi^idest range, 

 occurring both among the coral reefs of the equatorial regions, and, 

 to the north and south, beyond the temperate zone. The Mediter- 

 ranean affords species of Gorgonia, Corallium, and Alcyonium, besides 

 numerous Actiniae. The coasts of Britain have also their Alcyonia 

 and Actinias, and from far in the northern seas, come the Umbellularia, 

 and some other species of the Pennatula family. 



Among the coral-making Actinaria, the Madrepore and Astrsea 

 tribes are almost exclusively confined to the coral-reef seas, — a region 

 included between the parallels of 28° north and south of the equator, 

 — while the Caryophyllia family are spread as widely as the species 

 of Actinia. Several species of Caryophyllidte occur in the Mediter- 

 ranean, and others in the high northern seas, and they are met with 

 at depths of several hundred feet. They are also common among 

 the coral-reefs of the tropics. 



The Madreporacea and Astrajacea, with the Gemmiporidse, are the 

 principal constituents of coral reefs. The temperature limiting their 

 geographical range is about 68° F., this being the winter temperature 

 of the ocean on the outskirts of the reef-growing seas. The waters 

 sometimes sink to 66° or even 64°, but this appears to be a temperature 

 which they can endure, and not that in which they germinate. The 

 extremes which they will survive prove only their powers of endurance, 

 and do not affect the above statement; for their geographical distribu- 

 tion will be determined by the temperature which limits their powers 

 of germination. 



The temperature in the warmest parts of the Pacific varies from 80° 

 to 85°, and here Astrseas, Meandrinas, Madrepores, &c., are developed 

 with peculiar luxuriance, along with thousands of other strange and 

 beautiful forms of tropic life. From the above temperature to 72°, 

 does not appear to be too great a range for the most fastidious species. 

 At the Sandwich Islands, which are near the northern limits of the 

 coral seas, Porites and Pocilloporas prevail, and there are very few 

 species of the genera Astra^a, Mussa, and Meandrina, which are com- 

 mon nearer the equator. 



