436 Mr. H. J. Carter on 



for what is generally called the " mouth " or " osculum " in 

 a calcareous sponge, after the manner that this would be 

 applied to a sack ; and the word " cloaca " for the cavity to 

 which it leads explains itself; while the apertures on the 

 surface of the latter will be termed " holes," and that or those, 

 as the case maybe, which are seen to open into them, more or 

 less below the surface, the '' openings," that is of the chambers 

 or canals of the internal structure or that of the wall ; the 

 whole of which is precisely similar to corresponding parts in 

 the non-calcareous sponges. 



For the interval between the surface or cortex of the body 

 and that of the cloaca the term " wall" will be adopted; its 

 structure consists of empty spaces accompanied by a- variable 

 quantity of minutely cancellated tissue. The former will be 

 termed tubes, chambers, or canals, according to their shapes 

 respectively. Thus they will be called " radial chambers " 

 (radial tubes, H.) when they are more or less cylindrical or 

 prismatic, straight and extending directly across the "wall" 

 horizontally, from under the pores on the surface to under the 

 holes of the cloaca respectively, as in Grantia ciliata, Bk. ; 

 or they may be "subradial," that is more or less branched 

 under the same circumstances, as in our Hypograntia ; or with 

 no appearance of radiation at all, as in our Heteropia ; or with 

 the empt)^ spaces canalicular and branched, tree-like, as in 

 Teichonella prolifera ; while the minutely cancellated tissue 

 which accompanies them will be termed " parenchyma." 



Again, as regards the form and arrangement of the spicules 

 in the structure of the wall ; this, in his Sycones, has been 

 divided by Hackel into " articulate " (gegliederte) and " inar- 

 ticulate" (ungegliederte), that is respectively where tiie skeletal 

 structure of the radial chambers (tubes, H.) is entirely com- 

 posed of a number of small radiates about the same size, or 

 where it is formed by the simple extension across the wall of 

 the long shafts of large radiates, whose heads support the 

 cortex or dermal structure on one side and that of the cloaca 

 on the other, thus leaving horizontal intervals between them 

 which correspond to the radial chambers ; or these two forms 

 of skeletal structure may be mixed, /. e. where one portion of 

 the radial chamber is " articulated " and the other " inarticu- 

 lated ; " but in all cases the sarcode tympanizing the intervals 

 of these spicules to complete the chamber is pierced by inter- 

 communicating pores ; while in the subradial or branched 

 chambers and the still further divided forms, up to that which 

 is dendritic, the chambers, now as it were become canals, are 

 rendered continuous with one another by larger or smaller holes 

 of intercommunication, according to the species and the degree 



