SPONGE WEAVERS. 127 



recognise a colony of unnumbered workers, myriads 

 of monads, living in company, toiling for the benefit 

 of the commonwealth, and weaving a home for them- 

 selves in the great deep, enlarging, extending, and 

 increasing the colony day by day, it will simply be a 

 repetition, in another form, of the same story as told 

 by the zoophytes, the sea-fans, the sea-mats, and the 

 architects of the Coral Islands. 



" Each wrought alone, yet all together wrought 

 Unconscious, not unworthy instruments, 

 By which a hand invisible was rearing 

 A new creation in the secret deep." 



The entire sponge, in its living state, is enveloped 

 by a sort of skin or dermal membrane, coated in the 

 inside with sarcode, and strengthened in various 

 ways by fibrous tissue, or spicules. This membrane 

 has the power of opening and closing pores on 

 any part" of its surface, through which the animals 

 breathe, or receive nutriment. Beneath these pores 

 are large irregular cavities, which receive the water 

 imbibed by the pores, and convey it by an inward 

 current into the canals, which branch and ramify 

 through all parts of the sponge, becoming smaller 

 and smaller as they divide and recede. There is 

 always a double series of canals, those which convey 

 the water charged with nutriment, by an inflowing 

 stream, to the remotest parts of the sponge, and 

 those which collect the exhausted water, and transmit 



