132 TOILERS IN THE SEA. 



if any, direct fact in support of this supposition, it 

 is at least a plausible one, and would serve to account 

 for the presence of some forms of spicules, which 

 seem to be scarcely intended solely for strengthening 

 the fabric, or serving as a simple defence, but are 

 evidently adapted for such a purpose as has been 

 suggested. 



Important as it must be to the sponge colony to 

 protect itself, as much as possible, from its enemies, 

 and also to ensure a supply of nutriment in its fixed 

 position, it is of equal importance that provision 

 should be made for the continuance of the species 

 by the establishment of new colonies. For this 

 purpose sponges are by no means left deficient in 

 resources, and the result may be obtained by one of 

 three methods, each of which can be resorted to in 

 case of failure by the other. These three modes of 

 reproduction are (i) by means of ova or eggs ; (2) 

 by gemmation, or budding ; and (3) by the spon- 

 taneous division of the sarcode, or flesh. Taking 

 these three modes in the order in which they stand, 

 we commence with the reproduction by means of 

 ova, or eggs, as at once the most common and 

 universal in the animal kingdom. Here, again, 

 there are two modifications, for although the pro- 

 duction of eggs within an ovarium prevails in the 

 majority of cases, yet it is possible for eggs to be 

 engendered without a proper ovarium, although this 



