24 CORALS 



Clip in wliich the polyps rest), with its radial septa, and 

 even this character is sometimes difficult to recognise or 

 define. 



The Order provides the bulk of the corals of the world 

 at the present day. In variety of structure and in the 

 number of genera and species the Madreporaria exceed all 

 the other kinds of corals put together ; and it is in con- 

 sequence of this preponderance that some authors would 

 confine the expression " true corals " to those of Madre- 

 porarian origin and confer some other designation such as 

 "corallines" or "false corals" on corals of a different 

 Order. Such a plan, however, is historically unsound and 

 from a practical point of view^ inconvenient. 



The Madreporarian corals may be arranged in various 

 ways. In former times, when very little or nothing was 

 known about the characters of the polyps, the classification 

 was based entirely upon the characters of the corallum. It 

 has been found, however, that such a classification leads to 

 the grouping together of corals that are not closely related 

 to one another, and, conversely, corals that are closely 

 related are, in such a system, widely separated. 



A sound scientific classification should be based on a 

 knowledge of all the characters possessed by these animals 

 in both their hard and soft parts. Such a classification 

 will fluctuate as our knowledge, which is still very imperfect, 

 increases, and in that respect may cause some inconvenience, 

 but it is the only kind of classification that will express the 

 true relationship of these corals to one another. 



The more empirical systems of classification, based on 

 the characters of the hard parts alone, have some general 

 utility and educational value, because in most cases such 

 characters are the only ones that are available for the 

 student at home, and the study of such characters must 

 form the introduction to this branch of science. 



Proceeding on such a system, an examination of a good 

 collection of dried Madreporarian corals, such as may be 

 found in any large museum, shows that they may be arranged 

 in two groups. 



In one may be placed those that exhibit a large number 



