SPONGES. 
47 
which one might call an egg, but that it possesses the 
faculty of spontaneous motion. The larger extremity is 
covered with excessively minute cilia, by the waving 
motion of which, as by innumerable oars, it is rowed 
along through the water, exactly like one of those In- 
fusoria which we described in a former chapter, and 
for which it might readily be mistaken. It docs not, 
therefore, fall to the bottom of the sea as soon as the 
ejective impulse of the parental current is exhausted, but 
continues to shoot along, until, exerting apparently a 
power of choice, it meets with a suitable locality for its 
settlement. Here it lodges, spreads out an adhesive film 
of gelatinous matter, absorbs its now useless cilia, becomes 
stationary, grows by increase of its circumference, and 
soon develops all the structure, and exercises the func- 
tions, that characterised its parent. 
“It is curious,” observes Professor Jones, “to observe 
the remarkablo exception which Sponges exhibit to the 
usual phenomena witnessed in the reproduction of animals, 
the object of which is evident, as the result is admirable. 
Ihe parent Sponge, deprived of all power of movement, 
would obviously be incapable of dispersing to a distance 
the numerous progeny which it furnishes. They must 
inevitably have accumulated in the immodiato vicinity of 
their place of birth, without the possibility of their distri- 
bution to other localities. The seeds of vegetables, some- 
times winged and plumed for the purpose, are blown 
about by the winds, or transported by various agencies to 
distant places ; but in the present instance, the still 
waters in which Sponges grow would not have served to 
tiansport their progeny elsewhere j and germs, so soft and 
