Pore-area of Cliona corallinoides. 17' 



been taken, and in which the dermal web-like sarcode (c) with 

 its pores (c?), as delineated, still remain. 



Let us now turn our attention to the vent or larger aperture 

 of the dermal sarcode, which here, as well as in Pachymatisma 

 Johnstonia, Bk., is more or less constricted or covered {{. e. 

 commanded) by a diaphragm of the dermal sarcode, in like 

 manner as the pores, although in the latter both vent and 

 pore-area are themselves solidly fixed by the masonry of the 

 little siliceous balls of which the crust of Pachymatisma is 

 composed. By this means (that is, by the dermal sarcode) the 

 vent also may be opened or closed when required, in all the 

 sponges, as I have long since shown in the young Sjjongilla 

 (Ult. Struct. Spong. I. c). 



In Cliona corallinoides the whole area of the head (figs. 33, a, 

 36, h) is not always given up to the vent, but allows the latter 

 to occupy its centre (fig. 35, e), while the circumference still 

 presents the tentacle-like prolongations (J h h) and pores of the 

 dermal sarcode between them {d)] so that the head is com- 

 posed of the two organs, so far in combination. 



It is a common occurrence for the pores in most sponges to 

 be seen close to the border of the great vent ; but as the latter 

 is only the opening at the end of the canal of the excretory 

 system, the pores, although close to its border, do not neces- 

 sarily communicate directly with it, but are in connexion 

 with the areolar parenchyma beneath, which is thus outside 

 and surrounds this canal or aperture. 



Hence, for convenience, I have taken the same head for 

 illustrating the vent that has been drawn from the pore-area 

 alone (fig. 34), and have placed a large circular aperture in 

 the centre for this purpose (fig. 35, a), after which it will not 

 be difficult for the reader to supply the other and, perhaps, 

 more common form, where the vent alone occupies the whole 

 of the head (fig. 33, V). I have also in this figure inserted the 

 bristling arrangement of the ends of the pin-like spicules as 

 seen in the dried state (fig. 35, f) , which has been omitted in 

 the former, also for convenience. 



Thus, however much like the polype-head the pore-area 

 may be, the tentacle-like prolongations can only be considered 

 to bear a remote resemblance to the tentacles of a polype ; 

 and thus also we read in Prof. P. Harting's valuable memoir 

 on Poterion^ or " Neptune's Cup " (where the pore-area is si- 

 milar in structure to that of Cliona corallinoides^ and the in- 

 ternal mass in like manner composed of areolar cavities only, 

 without cawa/-system) : — " Peut-etre MM. Hackel et Miklucho- 

 Maclay verront-ils dans ces plis rayonnants [in the pore-area] 

 une confirmation de leurs id^es sur les affinit^s des Sponges 



Ann. & Mag. N. Hist. Ser.4. Vol. y'lii. 2 



