SPONGE WEAVERS. 135 



oval-shaped, and at length, in their mature state, 

 they acquire a regular ovate form." When fully 

 developed they separate from the parent, and pass 

 out with the outflowing current at the oscules. At 

 this period, Dr. Grant states, that they are endowed 

 with spontaneous motion, in consequence of their 

 larger extremity being furnished abundantly with 

 cilia, or very minute transparent filaments, broadest 

 at their base, and tapering to invisible points at 

 their free extremities. After floating freely for a 

 time, they become attached to some fixed body, 

 adhering firmly to it, and spreading themselves out 

 into a thin transparent film. When two of these 

 come into contact they unite, thicken, and produce 

 spicules, and in a few days there remains no line of 

 distinction between them, and they continue to grow 

 as one individual. Subsequently Dr. Bowerbank 

 confirmed these particulars, except as regards the 

 cilia in motion, and observes : " That a sponge is 

 not always developed from a single egg or bud, 

 but that, on the contrary, many eggs or buds are 

 often concerned in the production of one large 

 individual, a few days probably serving, by this 

 mode of simultaneous development, to form the basal 

 membrane of the sponge, of considerable magnitude, 

 as compared with the individual egg or bud, or 

 with a sponge developed from a single egg only." 

 As to his supposition that some of the buds are 



