396 Mr. Hogg's Observations on the Spongilla fiuviatilis, 



In the first place, as to the peculiar motion of sliding or creeping exhihited 

 by pieces of the Spongilla in the water, I have no doubt that much the same 

 may be seen on detaching portions of some plants belonging to the Ulcœ, 

 Fact, &c., when placed in that fluid, and that it arises from some other cause 

 than, that of such contractile and expansive powers as are known to pertain to 

 aninuil life. Indeed portions of some Fuci, especially of the leaves or fronds 

 of Fucus vesiculosus, F. serrafus, &c., I have been (hstinctly informed, on 

 being torn from the original plant and put into water, sliow tlieir edges roll- 

 ing up and forming wluit miglit be esteemed by some as a sort of contraction, 

 and in other respects varying and altering their newly-divided margins. And 

 in corroboration of this statement, I will here add tliese appropriate words of 

 Dr. Johnston: " I may remark on these experiments (of Dujardin), that loco- 

 motion is no proof of animality. Several Jlgœ are locomotive*." 



Now these changes in form of small parcels of the Lake Sponge are ac- 

 counted for by M. Dutrochet, l)y a " mouvement de transport des globules 

 élémentaires d'un lieu dans le lieu voisin ; ces globules vésiculaires ne sont 

 point immobiles dans leur adhérence mutuelle ; ils se meuvent les uns sur les 

 autres sans quitter leur adhérence par une sorte de glissement, et cela par 

 l'effet d'une force inconnue qui appartient au tissu vivant. C'est une action 

 vitale nouvelle qui joue certainement un des principaux rôles dans le phé- 

 nomène de l'accroissement en longueur des végétaux, accroissement qui est 

 quelquefois d'une rapidité singulière f." 



In the second place, the fikiments that M. Dujardin describes as being 

 " llagelliformes très longs d'une ténuité extrême," with which the pieces of 

 Spongilla lacustris are externally furnished, evidently appear to me to be 

 either the terminating capillary fibres j', which I have generally noticed grow- 

 ing beyond the surface of the membrane that envelopes the parenchymatous 

 jelly in the River Sponge, or else some species of a Cryptogamic plant, such as 

 a Conferva, or an Oscillaforia, &c., which has parasitically grown upon that 

 substance ; for I have constantly observed a Conferva-like plant with long, 



* Compare Johnston's Brit. Zooph., p. 323. 

 t See Annales des Sciences Naturelles, torn. xv. pp. 214, 21.5. 



X These will, I conclude, readily explain what M. de Lamarck means by " subpiliferis " and " |)ili- 

 fères," in his description of the Spongilla. See Anim. sans Vert,, torn. ii. p. 98, edit. 1816. 



