GENERAL STRUCTURE OF ZOOPHYTES. 17 



From each cup the extremity of a polyp protrudes itself with its 

 coronet of slender tentacles. 



The Actinoidea, which comprise all the common coral-forming 

 species together with the tribe of Actinias, include polyps of various 

 sizes, from the microscopic point to a diameter of eighteen inches. 

 The presence of internal reproductive lamellae, and the fact of their 

 ejecting the ovules by the mouth, separate them widely from the 

 Hydroidea. The tentacles are in one or more series, or scattered. 

 The coralla may be either calcareous or horny ; but the calicles, 

 when any exist, are always calcareous. 



In the remarks which follow, I shall be brief with the first order, 

 as my own observations can contribute little to what is already known. 

 Some general account of these animals is required in this place, to 

 serve for comparison with the Actinoidea, on which I shall dwell 

 more at length. 



