THE LOWER FORMS OF LIFE. 113 



Now, it follows as a matter of course that as the Coral is secreted by 

 the inner skin, it must, of necessity be inside the polyp ; and it 

 is called, by reason of its mode of formation, sclero-dermic, while 

 the number of tentacles, and therefore of partitions, is always five 

 or six, or multiples of these numbers. This mode of coral forma- 

 tion is also called by Dana "tissue secretion." In a living state 

 the Coral in this section is also hidden by the compound animal, 

 each polyp being connected by an extension of the internal layer of 

 skin, or coBnosarc. 



It is by Corals of this division that all reefs and most of the 

 specimens in our collections have been formed. If the reader will 

 take up one of the species which he may have in his possession, he 

 will observe that it is made up of a number of cells, having their 

 lamellae, or plates of carbonate of lime, crossing each cell in regular 

 order, and forming five or six partitions or multiples thereof. A single 

 cell of this kind is called a corallite, and several of these together a 

 corallum, while, just as the flesh which connects the polyp is called 

 a coenosarc, so the carbonate of lime which connects the corallites of 

 a corallum together is called a ccenenchyma (koinos, common, chyma, 

 tissue). The entire calcareous substance of a Coral is called 

 " sclerenchyma." It must be borne in mind that, however large the 

 corallum, it has been formed by successive layers of polyps. Life 

 and death, as in all organised nature, carry on their operations side 

 by side. Each layer of polyps, having fulfilled their allotted duty, 

 increase by budding or division, and die, while their progeny rear 

 up a new stratum of Coral upon their remains. And this process 

 goes on till vast masses of dead with a thin stratum of living Coral 

 on its surface are formed. Thus the result may be the specimen on 

 your chimney-piece, a small island, a reef 1000 miles long, or a vast 

 continent like that supposed to have sunk in the Pacific Ocean, 

 millions of square miles in extent. " What vast industry is here 

 exhibited ! " I fancy I hear some one exclaim. Not in the least. I 

 am sorry to destroy such an illusion, for, in fact, our friend the Coral 

 polyp is a bit of a sensualist, and passes his whole life with no 

 care of the morrow and no thought of the past. The whole object 

 of his life is to secure food and open his flower-like tentacles and 

 bask in the blue waters which are warmed by the tropical sun. The 

 Coral is made without the slightest effort on the part of the polyp. 

 It is secreted just as our bones are secreted, whether we will or no. 

 It is a process of life, guided by the laws of life, and perfected by 

 the forces of life. But notwithstanding, as we shall hereafter see, 

 this humble organism, like the Amoeba of the Laurentian rocks, has 

 been a mighty architect in Time. 



Let us now examine into the minute structure of Coral, and take 



