KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 32. N:0 I. 9 



By the latter passage, compared with the foi'mer statement, and also by others in theii- 

 works may be seen that they had in view different sorts of coenenchyma, so amongst 

 others a false one or a peritheca as in Galaxea, with which also the perithecal secretions 

 in the palaeozoic genera Syringophyllum and Pholidophyllum may be compared. 



Since MiLNE Edwards and Haime had published their memoirs on the structure 

 of the corals the term coenenchyma was ahnost generally accepted by authors writing on 

 x\nthozoa. But theve has, of course, been great diiference of opinion concerning its na- 

 ture and some have even interpreted it in a sense contrary to the meaning of those first 

 authors. In all variance of opinion is to be fouud a tendency to regard as coenenchyma 

 all interspace between not too closely set calicles. In this wide conception it is, of course, 

 evident that the denomination coenenchyma- must embrace a great multiplicity of highly 

 different structures. The coenenchyma in the Antipatharia cannot of necessity bear the 

 slightest resemblance to that of the Madreporaria. It may then be justly said that it exists 

 as many kinds of coenenchyma as there exist groups or large divisions of genera. Duncan ^ 

 was right when he said that all sceletal structures outside the true theca were to be 

 called exotheca, but, when he continues that this was of two kinds 1) coenenchyma and 

 2) peritheca, a difficulty arises to discern between them. It might be said that the peri- 

 theca is without any intimate connection with the calicles, lies outside theui, as in Gal- 

 axea, the coenenchyma again is in intimate connection with the calicles or indeed only 

 a part of them. 



As to the coenenchyma of the Heliolitida?, the particular objects of this my uiemoir, 

 the following most important interpretations of its nature have hitherto been given. One 

 of the most remarkable opinions is that advanced by Nicholson. Probably the singular 

 tubular composition of the coenenchyma in the genus Heliolites has given the first im- 

 pulse to his views. 



The first origin of this hypothesis can be traced to a paper, read by him'- March 1875 

 and published in the same year. He there, treating of the calicles and the coenenchymal 

 tubes of the genus Heliolites and its palaeozoic allies says that »the question arises .... 

 whether these (coenenchymal) tubuli are to be regarded as constituting a proper coenen- 

 cliyma, or whether they are not really of the nature of aborted or rudimentary corallites». 

 And he thinks that several facts not nearer mentioned favour the latter view. Not long 

 afterwards Moseley sent to the Royal Society a paper on Heliopora ^ in which he ex- 

 pressed nearly the same opinion, without, of course, being aware of Nicholson's shortly 

 before published views. In this paper Moseley compares the polyp animals of Heliopora 

 with those of Sarcophyton, in which Alcyonarian there exists a dimorphism of two diffe- 

 rent sets of polyps: sexual animals and zooids, which latter are by far more numerous 

 than the former. Moseley thought '^ it »by no means improbable that the coenenchym 



1 Revision p. 202. 



^ On the mode of growtli and increase amongst the Corals of the Palaeozoic Period. Transact. R. Soc. 

 Edinb. vol. XXVII pt. III, p. '248. 



^ Structure and Relations of the Alcyouarian Heliopora coerulea etc. rcceivd by the R. Soc. Sept. 28"', 

 read Novemb. 25*'' 1875 and published 1876 iu vol. 166 pt. 1 of Träns. R. Soc. This paper was published 

 again, a little enlarged, in the »Report on the Corals» in the »Results of the Challenger Expedition, Zoology » 

 pt. VII of vol. II. 



* 1. c. p. 119. 



