30 NATURAL HISTORY OF OUR SHORES 



so often alluded to as " Coral Insects." The corals belong 

 to the division Anthozoa. 



Each consists of a circular column, which is hollow, and 

 has its upper margin fringed with one or more rows of 

 hollow, finger-like tentacles. These tentacles are some- 

 times short and stout (in Tealia, etc.) ; sometimes long, 

 slender, and " snaky " (in the " snake-locked anemone " 

 Anthea) ; oftentimes fine and feather-like (in Dianthus, 

 etc.). Each of these we shall survey presently. 



These tentacles are retractile, and when the column folds 

 inward at the top they are out of sight. 



On the upper part of the column, within the rows of 

 tentacles, is the disc ; in the centre of this is the mouth, a 

 slitlike opening ; and from this, in the inside of the column, 

 but not extending to the bottom, is a membraneous tube, 

 corresponding to an oesophagus, which opens into the 

 cavity below. 



From the inner wall of the column, radiating towards the 

 centre, and attached to the oesophagus as far as it reaches, 

 are a number of membraneous partitions, termed mesenteries. 

 These divide the column into a number of triangular 

 chambers from top to bottom. 



Attached to, and between, these membranes are a number 

 of glands, reproductive and other. 



There are no internal organs in the usual sense neither 

 stomach, intestine, heart, or breathing organs ; hence the 

 term coelenterata. 



Most species attach themselves by the base of the column 

 to rocks or other objects, but one or two forms live, worm- 

 like, in the sand, from the surface of which they protrude 

 their circle of tentacles (Peachia, etc.). 



One species on our shores secretes lime from the sea, and 

 builds itself a skeleton around its column, and following 

 the course of its mesenteries, thus constituting itself to all 

 intents and purposes a coral, representing the mighty hosts 



