20 
GUIDE TO THE CORAL GALLERY. 
High Cases 
I.-VI. and 
Table Cases 
1 and 2 A. b. 
PORIFERA [SPONGES], 
[The High Cases are indicated by Roman numerals and the shelves of the 
same by Arabic numerals.] 
Introduction. 
The term “ sponge ” is popularly associated solely with the soft 
elastic hath sponge, but a glance at the Cases will show that, in 
zoology, the word has a much wider meaning, some “sponges” 
being of stony hardness, others leathery, others again like spun glass. 
In life, the bath sponge is tough and fleshy, and covered with a 
black skin (Case I., specimen in fluid). A section (Fig. 18) shows 
a light-coloured flesh in which no trace of the horny skeleton, 
commonly known as the sponge, is apparent ; to obtain this the 
skin and flesh are macerated off, leaving the more resistant skeleton. 
It would be instructive here to notice the glassy skeleton of 
Euplectella aspergillum , or Venus’ Flower-Basket (Cases III. 2), and a 
complete specimen of the same in fluid (Table Case 2a) ; here again 
the skeleton is concealed by the soft tissues. The dried specimen of 
Euplectella imperialis (Case III. 3) shows the fluffy-looking soft 
tissues above and the denuded skeleton below. 
Many specimens, especially those in Cases IV.-VL, do not 
materially differ, excepting in colour, from their appearance in life. 
The position of Sponges in the Animal Kingdom is above the 
Protozoa or Simplest Animals and near the Coelentera (Zoophytes, 
Corals, &c.). 
To give some idea of the structure of a sponge, a brief account is 
given of ffalichondria panicea, the Crumb-of-Bread Sponge, common 
round the British coast (Case IV. 3). 
This sponge forms yellow or greenish crusts on rocks, or shapeless 
masses round the stems of sea-weeds. The surface of incrusting 
specimens is usually covered with crater-like orifices termed oscules. 
On closely observing living specimens in a large vessel of sea-water, 
currents, rendered visible by debris, will be seen coming out of the 
oscules ; a little indigo or carmine will serve to render the currents 
still more apparent. 
