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 does 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 Jon os, "to observe 

 the remarkable 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. 

 The 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 immediate 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 

 transport their progeny elsewhere ; and germs, so soft and 



