SYCANDRA, 103 



CHAPTER XII. 

 TYPE OF PORIFERA. 



SYCANDRA. 



Phylum Porifera. 



Class Calcarea. 



Sycandra compressa is a small marine p- _sycandra 

 sponge of a dull yellow tint, found fixed ^' Compressa. 

 to rocks or weeds between tide marks. Oscuium 

 Form and ^^ '^^ ^"^ shape like a fiat- 

 Habits. ^^^^\ ^^'^ ^^^, ^.^'^/"g ^^ , r 



length up to If mch. It / ^ Bud. 



is like all sponges axially symmetrical 



(though the symmetry is often obscured), 



hence we can distinguish merely a main 



axis, a base, and an apex. The base is 



fixed to a foreign body and the apex 



has a large opening, the oscuhcm^ ^^hich ^'^^^^ t° s^^-^^^^' ^^^^ ^^^ » 



leads into the interior of the sponge. natura size. 



If the living Sycandra be watched carefully in a vessel of 

 water, it will easily be seen that currents of water are, with- 

 out intermission, pouring out of the oscuium. Further 

 examination of the surface of the sponge would reveal an 

 immense number of extremely minute openings all over the 

 surface, into which the water perpetually flows. These are 

 termed \}(\^ pores. 



If a hand-section of the sponge be made it is seen 

 to be hollow, and the wall appears of even thickness all 

 round the central cavity. This cavity is called the para- 

 gastric cavity, opening through the oscuium to the exterior. 



The walls of the sponge are of a somewhat firm leathery 

 Internal consistency and when boiled in potash the 

 animal matter is destroyed, leaving a residue 

 of numerous small spicules, transparent and 

 tri-radiate in shape. These hard spicules dissolve immedi- 

 ately, with effervescence, on the application of any dilute 



