6 
the whole colony hard and soft parts together, the word Coenosteum to signify the hard coral 
skeleton only. The word Coenosare refers to the system of canals and superficial ectoderm 
connecting the zooids of the colony, the words Gastrozooid and Dactylozooid refer to the soft 
parts of the zooids only. With reference to the word “Coenenchym” frequently used by ‘writers 
on Madreporaria, Hydrocorallina and Alcyonaria a few remarks here seem appropriate. 
The word seems to have been introduced by Mitne Epwarps and Hate and the 
following sentence from their chapter of general considerations on the organisation of corals 
explains clearly the sense in which they used it’). ‘Il existe par conséquent la un tissu commun 
ou coenenchyme qui précede existence des individus et qui joue un role considérable dans la 
constitution du polypier, ainsi que nous le verrons par la suite’. 
The word is used in a similar sense by KOLLIKER *) who speaks of de LacazeE Duruiers 
discovery that the axis of the precious coral is formed by ‘einer Verkalkung der inneren 
Lagen des Coenenchyms” and by many other writers. 
Originally then the word referred to soft tissues only. Writers on Alcyonarians at the 
present day use it for extra-thecal parts of a colony, i. e. hard spicules and soft tissues 
together, exclusive of the solidified axis. Writers on Madreporaria have however come to use 
the word in a different sense altogether so that we read in a recent paper on Madreporaria. 
“By universal acceptation coenenchyme is the calcareous deposit originating from the coenosarc’’®). 
This is neither historically nor philologically correct. The sense in which the word Coenenchym 
should be used and is used by us in this memoir is as the expression for the superficial hard 
and soft parts beyond the limits of the zooid pores. 
Stylaster Gray. 
The genus may be defined as follows: 
Coenosteum arborescent usually flabelliform. Pores in regular cyclosystems only. Style 
in gastropores and dactylopores. Dactylozooids can be only partially retracted. Ampullae usually 
prominent in both male and female stocks. Male gonophore with an endodermic spadix, four 
to five gonophores in each male ampulla. 
This definition differs from that of MosELey in several respects. The difficulty which he 
originally pointed out of separating Stydaster from AZlopora has not been overcome. Speaking 
generally the colonies of AZ/opora are more robust in habit and do not show such prominent 
male ampullae at the surface as are usually found in Stydaster. The male and female gonophores 
of the two genera are very similar in detail but, from the limited number of forms investigated 
at present, it appears probable that in the species of Stydaster there are more gonophores 
(4—5) in each male ampulla than there are in d//ofora. And as the male gonophores are 
more deeply seated in AZ/opora than in Stylaster the tubular spout of the testis is longer and 
more definite in the former than in the latter genus. Mosetey thought that a difference might 
1) MitneE Epwarpbs and Harmer. Hist. Nat. des Coralliaires. t. 1, p. 29. 
2) A. K6OLLIKER. Icones Histiol. p. 117. 
3) J. E. DuerpDEN. Mem. Nat. Acad. Sci- VIII, 1902. 
