1886.] 



POSITION AND CLASSIFICATION OF SPONGES. 



573 



we have Ceraospongise before us. Transitional forms between the 

 Cornacuspongiae with supporting spicules cemented by spongin, and 

 Cornacuspongise without spicules in their fibres (horny sponges), 

 are not unfrequent. 



One whole subfamily, the Chalininse, comprising nearly 300 species, 

 is composed of such transitional forms. The supporting spicules met 

 with in the Cornacuspongise are invariably monaxon without a 

 swelling at one end. Besides these more or less rod-shaped sup- 

 porting spicules, we also find in some of the Sponges belonging 

 to this group so-called flesh-spicules — small, irregular curved or 

 complicated elements scattered throughout the Mesoglcea. These 

 occur associated vnth spicules in the fibrous supporting skeleton 

 and also in those forms which have no spicules in their horny 

 supporting skeleton. To this group also the genera Halisarca and 

 Bayalus belong, which have no skeleton at all, and appear as 

 askeletous forms of the Aplysillide type. The term Cornacuspongise 

 was established by Vosmaer(1550), and used by him in a very similar 

 sense to that in which it is used here. The group Chondrospongise, 

 on the other hand, is in the sense given above a new one ; it nearly 

 coincides with Vosmaer's group Spiculispougise (1550). In a former 

 paper (889) I had retained the group Myxospongise, for the sake of 

 convenience, preliminarily only, and agreeing at the time with SoUas 

 (1440) that it was unnatural. The manner in which I have distri- 

 buted the members of the Myxospongise among other groups is in 

 accordance with the view expressed by F. E. Schdze in a letter. 



We have accordingly to divide the subclass Silicea into three 

 groups in the following manner : — 



Subclassis SILICEA, Lendenfeld. 



Mesoglcea soft ; support- 

 ing skeleton olten strength- 

 ened with siliceous cement. 

 Spicules triaxon. 



Ordo HEXAOTI- 

 NELLIDA, 

 O. Schmidt. 



Mesoglcea hard ; tough- 

 ness achieved by the hard- 

 ening of the ground-sub- 

 stance. Spicules tetraxon, 

 monaxon, anaxon, or ab- 

 sent ; generally corticate. 



3. Ordo CHONDEO- 

 SPONGI.E, 

 Lendenfeld. 



Mesoglcea soft ; support- 

 ing skeleton strengthened 

 by spongin cement ; or 

 exclusively formed of 

 spongin, with or without 

 foreign bodies. Spicules 

 monaxon, or absent. 



4. Ordo CORNACU. 



SPONGLE, 



Vosmaer. 



Expressed in the usual manner, the class Spongise would be 

 accordingly divided intoyoMr Orders in the following manner:— 



Classis SPONGIiE, auctorum. 

 Coelentera with branching canal-system, without movable appen- 

 the organs of which are developed from cells of the mesoglcea. 

 With simple epithelia. 



I. Subclassis OALCAREA, Grant. 

 Spongige with a skeleton composed of spicules which consist 

 chiefly of carbonate of lime. 



