298 THE PROCEEDINGS OF THE LINNEAN SOCIETY 



corallite and should be placed between certain septa and the 

 columella, or the anal space, when this last is deficient ; they may 

 adhere to the septa, but in either case the ornamentation and 

 general arrangement of the sclerenchyma of the pali differ from 

 those of the septa ; a row of pali infers an extra row of tentacles. 

 But the term pali is given to prominent dentations of the inner 

 margins of septa, or to the inner margins when their dentation 

 differs from the rest of the septa as in Phyllangia, for instance. 

 This is not correct ; such structures may be called papillose, but 

 this will not permit of the corallites being classified as having 

 pali." In another place, the same author says, (p. 432) : — " The 

 importance of deciding the true character of the structures is 

 great, for whilst the septal spine may be of specific importance, 

 the presence of the pali as independent structures is generic, for 

 it involves the presence of other tissues ; such for instance, as 

 an extra crown of soft tentacles. Every one who has seen many 

 of the small sessile corals usually called Astrangia, Phyllangia and 

 Ulangia, amongst the Astrav giacea: must have felt this difficulty. 

 In some, the spinose character of the false palus is evident, but 

 in other species an arbitrary custom appears to have decided that 

 such and such are not septal structures but pali." 



It seems to me that there is almost the same difficulty in a 

 different way as to the columella, as I have before remarked, and 

 so also as to the costae which are sometimes clearly only extra 

 mural septa, and sometimes quite distinct from other tissues. 

 A good many of the difficulties might be met for the present by 

 most exactly defining the terms and introducing a few new ones. 



I propose to follow up this paper by another on the corals of 



the Chevert Expedition, which will principally include tropical 



forms. 



The Class Polyps, to which Corals belong, comprises radiated 



aquatic animals which have only one orifice which is surrounded 



with tentacles, the body being hollowed out, and forming open 



and intercommunicating cavities in which are contained the 



reproductive organs. 



The class is divided into sub-classes, namely — 1. Cnidaria,* 



* From icvidri, applied by Aristotle to the Jelly Fish, which he also 

 called a.Ka\r)<fn]. 



