36G il//-. Hogg's Observations on the Spongilla fluviutilis. 



stantly seen specimens of this Spongilla of various sizes and gradations, and 

 to all appearance as if they had originated or been produced from tliese sin- 

 gular seedlike bodies. Moreover, last March, having procured some of these 

 fresh bodies, I placed them in a glass vessel, nearly filled with spring water, 

 and changed tlie water every day ; six of them soon affixed themselves to the 

 bottom of the glass*, and in about three weeks every one of them was covered 

 with a whitish and wooll-like substance, which I took for the rudiments or 

 commencement of the Sponge t- After that time I was obliged to leave 

 home, and consequently to give up all further investigations upon that in- 

 teresting subject. 



I ought also to inform you, that I find from experiment these seedlike 

 bodies, when dried and long kept out of water, exhibit no such appearances, 

 and seem, when replaced in water, as if they had lost all their vitality and 

 power of reproduction ; neither have I perceived that they possess, even in a 

 fresh state, any cilia nor any locomotive property;}: whatever, wherein they 

 essentially differ from the similar germs, or ovules, or sporules, of certain spe- 

 cies of the Sea Sponges, as described by Dr. Grant '^. 



Pallas in a note to his description of Spongia Jiuviatilis (p. 385. " Elenchus 



* This glass vessel, with these same specimens, was exhibited to the Society on December 18th, 

 183S. Upon examining the small white patches with a lens, they were found to be the true rudi- 

 ments of the Spongilla, having the cells or pores very distinct, and formed by the little anastomosing 

 fibres or spicula. 



t A short time after this letter was read, my attention was called by m)' friend Professor Bell, to 

 Mr. Gray's paper (with which I was previously unacquainted) in the Zool. Journ. vol. i., where at 

 p. 50 I noticed that he mentions squeezing the granules from some specimens of freshwater Sponge, 

 and adds, " There were a few partly decayed leaves at the bottom of the basin, on which the green 

 granules fell. Being called away, I left them there for a day or two, when on m)' next examination 

 I found they had formed a more velvety mass, through which visible fibres were shooting, which gra- 

 dually enlarged, thus growing entirely after the manner of vegetables." This is a pleasing confirma- 

 tion of my own experiment. 



\ Nor has M. Dutrochet noticed the power of locomotion in the similar bodies which belong to the 

 Spongilla lacustris. His remark is as follows : " Enfin M. Grant a fait cette observation neuve et 

 curieuse que les corps oviformes, ou les œufs de l'Eponge, lorsqu'ils sont détachés et devenus libres, 

 sont animés de mouvemens spontanés comme des animaux. Je n'ai point fait cette observation sur les 

 corps oviformes de la Spongille, que je regarde comme des sortes de tubercules." Vide Annales des 

 Sci. Nat. tom. xv. p. 217. 



§ Vide p. 382. vol. xiii. of the Edinburgh Philosophical Journal for 1825 ; p. 154 of the Edinb. 

 New Phil. Journ. for 1826 ; and p. 129 of the same Journal for 1827. 



