138 TOILERS IN THE SEA. 



represents a coherent aggregate of monadiform 

 swarm-spores, or, as it may be most appropriately 

 denominated, a ' swarm-gemmule.' In their most 

 characteristic form these reproductive bodies, or 

 cell aggregates, consist of a uniform series of col- 

 lared zooids." Forms are minutely described under 

 about three types, as encountered in different species 

 of sponge, but they agree in all essentials, as an 

 aggregation of flagellate collared zooids, following 

 the pattern of their parent. 



Having now, somewhat imperfectly, sketched the 

 outline of the structure, and economy, of a rather 

 obscure but very large section of "Toilers in the 

 Sea," we cannot dismiss them, humble as they are 

 in their sphere and vocation, without calling atten- 

 tion to some of their ' beauties, which must appeal 

 even to those who are wearied by details of their 

 growth and development. It has been shown that 

 there is in all a fundamental skeleton, of a horny, 

 flinty, or chalky substance, held together and sur- 

 rounded by the living flesh, or sarcode, of the 

 animal, that this skeleton is secreted by the vital 

 elements from the sea in which it dwells, that the 

 sponge continues to grow, by aid of the sustenance 

 it obtains from the water, that it contains ample 

 provision in various ways for the reproduction of 

 the species, and that some portions of the structures 

 so elaborated are practically indestructible, and may 



