6 OCEAN LIFE. 



monade-like bodies, nearly all of the same size and form, resemble 

 the pellucid granules or vesicles, which Trembley has represented 

 as composing the whole texture of the Hydrse, or the soft granular 

 matter we observe in the stems of living Sertularise ; and, indeed, 

 most of the fleshy parts of organized bodies appear to be com- 

 posed of similar pellucid, granular, or monade-like bodies in dif- 

 ferent states of aggregation." The composition of the skeleton 

 or fibrous portion of the Sponge is remarkably diversified. Its 

 liquid food is not received into any cavity, but permeates to all 

 points, and is equally elaborated in every part of the system, 

 which, in one sense, is an unconfined digestive cavity, where the 

 various ingredients are selected, separated, and fitted for appro- 

 priation by each species, agreeably to its nature. For example, 

 it is very common to find growing on the same rock or sea weed, 

 a siliceous, a calcareous, and a horny sponge ; they have all the 

 same exposure, and are all recipients of the same nutriment, yet 

 does each act upon this differently. One extracts from the fluid 

 silica, which it causes to assume a solid crystalline form ; another 

 selects, in the same manner, the calcareous particles which obe- 

 dient to the laws of life, assume figures novel to them in their 

 mineral state ; and, again, another rejects both the lime and 

 the flint as injurious to its constitution. Sponges appear to be 

 true Zoophytes, and it imparts additional interest to their study 

 to consider them, as they possibly are, the first matrix and cradle 

 of organic life, and exhibiting before us the lowest organizations 

 compatible with its existence. 



Dr. Grant, to whom we are chiefly indebted for the physiology 

 of Sponge, was the first to establish the fact of a continued cur- 

 rent (except when interrupted by the will of the animal,) moving 

 from without into the interior of its body, and thence passing 

 through large channels to find an exit by the oscula or mouths 

 again, from the exterior surface. Dr. Grant observes : " I put 

 a small branch of Spongia coalita, with some sea water, into a 

 watch glass, so as to bring one of the apertures on the side of 

 the Sponge fully into view under the microscope, and I beheld 

 for the first time the splendid spectacle of this living fountain 

 vomiting forth, from a circular cavity, an impetuous torrent of 

 liquid matter, and hurling along, in rapid succession, opaque 



