STEUCTURE OF SPONGE. 23 



rounded. On a little indigo being diffused in the water, it was seen to 

 be absorbed with avidity ; and the inhalant action continued for a con- 

 siderable period, the interior of the sponge becoming strongly coloured 

 with indigo. 



After a time the rapid inhalant process ceased, either abruptly or 

 gradually, a very languid action only remained, and nearly the whole 

 of the pores were closed. When this operation was about to take place, 

 the rounded margin of the orifice lost its form and became thin and 

 sharp, while the circumference gradually melted inwards until the ori- 

 fice entirely closed, and not a vestige of the organ previously existing 

 remained : the operation of closing occupied rather less than a minute. 

 When once closed, these orifices do not appear to be reopened, but fresh 

 pores are produced. The colouring matter absorbed during the period 

 of active inhalation was apparent in the sponge from twelve to eighteen 

 hours ; and during this period the stream from the osculum was ex- 

 tremely languid. The structure and habits of the freshwater Sponges 

 are entirely in accordance with those of marine species. 



(51.) Prom this description of the structure of a sponge, it will be 

 apparent that all parts of the mass are similarly organized : a necessary 

 consequence will be, that each part is able to carry on, independently 

 of the rest, those functions needful for existence. If therefore a sponge 

 be mechanically divided into several pieces, every portion becomes a 

 distinct animal. 



(52.) In Cliona celata, one of the freshwater sponges, M. Dujardin* 

 discovered, mixed up amongst the pin-like spicula that constitute their 

 skeleton, irregularly shaped globules, composed of a contractile gluti- 

 nous substance, which, when examined under the microscope, were 

 seen continually to change their shape, presenting a constantly varying 

 outline, exactly similar to what is witnessed in the protean animalcule, 

 Amceba diffluens, above described ; and to this contractile substance, 

 whereof the living substance of the sponge seems principally to consist, 

 he proposed to give provisionally the name ofHalisarca (sponge-flesh f). 

 Subsequent observations have shown that these proteiform bodies are not 

 only thus changeable in their shape, but are able to exercise a distinct 

 power of locomotion by agitating long flagelliform filaments that are 

 appended to their bodies (fig. 11, l) ; in fact, the whole of the living 

 portion of the sponge seems to be made up of agglomerations of these 

 amorphous bodies, spread over the spicula or skeleton of the sponge, all 

 individually capable of changing their form by emitting processes in 

 different directions, so as to increase their means of contact with the 

 surrounding fluid, from which they evidently derive materials for 

 assimilation. 



(53.) These sponge-cells, as they are called by Mr. Carter , are about 



* Ann. des Sc. Nat. torn. x. 1838. t Lit. " sea-flesh." 



} On the Freshwater Sponges of Bombay. Ann. Nat. Hist. 1849. 



