PORIFERA [srONGES]. 21 
The origin of these sponge fountains had always been a profound High Cases 
enigma, which Dr. Grant quaintly compared to that of the then Table Cases 
mysterious sources of the Nile. In 1825 the above-named zoologist 1 and 2 a. b. 
observed small particles being carried by currents through minute 
pores in the general surface of the Halichondria (Figs. 2, 3b) ; and 
on account of the presence of these pores, he gave the name Porifera 
to sponges. So much for the entrance and exit of currents : to 
ascertain their complete course and their cause, it is necessary to cut 
very thin slices of the sponge (Fig. 3). The pores (Fig. 3b) lead 
into spaces and channels, which are more or less branched, and which 
finally arrive at the outer surface of groups of spherical cavities 
termed flagellated or whip chambers, each of an inch in 
Fig. 2. 
Halichondria panicea (after Dr. Grant), a, pores ; e, oscule ; /, ova. The out- 
ward arrows show the currents escaping by the oscules ; the iuward ones 
water entering the pores. 
diameter, and with minute orifices in their walls. The whip 
chambers open each by a comparatively large orifice into channels of 
spaces ; these join with others to form larger and larger canals, 
which terminate in an oscule. The whip chambers are lined with 
“ collar-cells ” (Fig. 3c), each of which is provided with a flagellum 
or whip and a hyaline collar ; the beating of the whips sets up the 
currents, which bring in food-particles and oxygenated sea-water, the 
used-up water and debris being driven out through the oscules. 
Food-particles are taken up bodily by the cells lining the walls of 
the canals and by the collar-cells ; but not much is known on this 
subject at present. The canal system from the pores to the 
whip chambers is termed “ in-current,” and that from the whip 
chambers to the oscules “ out-current.” 
