386 Mr. Hogg's Observations on the Spongilla fluviatilis, 



causing all those temporary, and apparently spontaneous, movements both in 

 the seeds or sporules*, and in the granules of vegetables. 



Wherefore it is manifest, that the very similar movements of the sporules 

 belonging to many water-plants, and of the gemmules of Zoophytes, are not 

 effected by the same means ; yet, nevertheless, tlie design and object of such 

 movements are without doubt the same, namely, a proper dispersion of the 

 different species throughout " the waters of the deep," and thus evincing a no 

 less wonderful than a beneficent mark of an Allwise Power, in providing for 

 the continuation and safe increase of even the most minute objects of created 

 being. 



Again, let me proceed to enumerate to you certain other facts which have 

 come under my observation tending to prove the vegetable nature of the 

 Spong ilia Jluviatilis. 



The first, that I must mention, is the resemblance of the membrane which 

 clothes the soft portion or jelly, and entirely lines the pores and canals of that 

 Sponge, with that of the leaves of plants ; this membrane or cuticle is ex- 

 tremely thin, delicate, transparent, and colourless, and seemed under the mi- 

 croscope which I used as if most finely reticulated. I examined with care the 

 membranes of the leaves of many common plants, amongst wiiich were the 

 daisy, cabbage, stock, primrose, lettuce, geranium, spinach, and thick-leaved 

 saxifrage, and to me their general similarity of appearance both in texture 

 and in transparency with the membrane of the Spongilla was obvious. Though 

 whether the delicate membrane of the latter be cellular, as Amici states is the 

 case with that of leaves, or merely porous, or not, I have been as yet unable 

 to discover by reason of my not having at hand a sufficiently high magnifying 

 powerf. 



M. Dutrochet has described in the valuable memoir before quoted, the 



* It is not unlikely that a number more of the seeds both of freshwater plants (Hydrophyta) and of 

 marine plants {Thalassiophyta) will hereafter be discovered to possess, for a short time, the like loco- 

 motive property. 



t I suspect, however, that if this membrane of the Spongilla were examined under a more power- 

 ful microscope, it will be found to possess a minuter resemblance with the external membrane of the 

 leaves or fronds of the Fttci. 



