11.6 POPULAR ILLUSTRATIONS OF 



v" 



observed to proceed from the external coat (b) to the axis (c). These 

 are termed septa, and are merely the calcified plates of the Actinia 

 which were illustrated in the last chapter. Just, however, as we saw 

 in the sea-anemone that the "mesenteries" were of different classes, 

 first, second, and third by reason of their falling short, more or 

 less, in passing through the somatic cavity, so do the septal plates 

 of Coral, as seen in the diagrams, differ in size just as they approach 

 more or less near to the axis. Some are seen to go from the theca 

 to the columella ; others stop short, as shown in both sections by the 

 dotted lines (h). Where the plates, however, stop short, their place 

 is supplied by pillar-like deposits, termed "pali," which, being 

 arranged necessarily in circular rows, are sometimes called coronets. 

 Some of the septa go through from one side of the corallite to the 

 other, as seen at f, Fig. 150 (p. 115), without touching the axis. 

 These are called " tabular dissepiments." Sometimes again, the 

 " loculi " formed by the septa are crossed by processes, or " styles," 

 called " synapticulae," which are seen at e, Fig. 151 (p. 115). These 

 are called " interseptal dissepiments." I have placed the lines across 

 at e, e (Fig. 150), just to signify the fact, but of course they would 

 not be seen in this section as shown in the diagram. The natural 

 primary division of all zoantharian or sclero-dermic Corals is into 

 six loculi by six septa. Secondary septa divide these into twelve, 

 and tertiary septa again divide these into twenty-four, which is the 

 number I have represented in the diagram 151. If any further division 

 occurs the law now alters, and the polyp only produces twelve 

 additional septa, being two for each primary loculus. 



Such, simply, is the structure of Coral. Mark, however, that no 

 single corallite or species of Coral possesses all the parts as shown in 

 the diagrams. Some have one kind of dissepiment, some another ; 

 some have "pali," others have none. A diagram not being a 

 drawing, we may take the liberty of making it useful by crowding 

 into it all the forms which are more or less assumed by different 

 Corals. 



When the systematist steps in, he classifies according to the 

 arrangement of these parts, and makes out a vast number of genera 

 and species, which fall not within the scope of this work. 



The forms thus assumed by Corals are various. I copy the 

 following descriptions from Dana's "Structure and Growth of 

 Zoophytes " premising that in a work recently published this 

 descriptive and beautiful passage is adopted without even quotation 

 marks or acknowledgment : 



" Trees of Coral are well known : and although not emulating in 

 size the oaks of our forests for they do not exceed six or eight 

 feet in height they are gracefully branched, and the whole 



