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XXII. Further Observations on the Spongilla fluviatilis ; with some Remarks 

 on the Nature oj the Spongise Mariuoe. In a Letter to the Secretary. By 

 John Hogg, Esq., M.J. F.R.S. L.S. 8^ C.P.S. 



Read December 18th, 1838; and June 4th, 1839. 



As I had an opportunity during this last summer of making additional 

 researches on the River Sponge, I think it necessary to lay before the Lin- 

 nean Society some further observations relating to that substance, in order 

 to correct, to elucidate, and to confirm several passages in my former letter, 

 and likewise to add a few remarks upon the nature of the Sea Sponges. 



In the first place, I ought to mention to you that I \ras not aware, until 

 some time after my last communication had been submitted to the Society, 

 that there are other eminent naturalists, besides Dr. George Johnston, who at 

 this day advocate the vegetable nature of all Sponges; and these I understand 

 are. Dr. H. F. Link, Professor of Botany at Berlin ; Dr. J. Miiller, Professor 

 of Anatomy at Berlin ; and Mr. J. E. Gray, of the British Museum. Of whom 

 the several opinions may be examined in the following works : Transactions 

 of the Royal Academy of Sciences at Berlin for the year 1830, Berlin, 1832, 

 p. 109. " Uber die Pflanzenthiere iiberhaupt und die dazu gerechneten Ge- 

 waschse besonders," von H"^" Link. "Annales des Sciences Naturelles, Seconde 

 Série, tom. ii. Botanique,"" Paris, 1834, p. 328. " Sur les Zoophytes en général 

 et en particulier sur certaines Plantes qu'on a confondues avec eux," par 

 H. F. Link ; being a translation of part of the former memoir. Mûller's 

 "Elements of Physiology," translated by Dr. Baly, Lond. 1838, vol. i. p. 42. 

 And the "Zoological Journal," Lond. 1824, vol. i. p. 46, 'On the situation 

 and rank of Sponges in the scale of Nature,' &c., by Mr. J. E. Gray. 



Also, MM. Dutrochet and Gervais consider that the Freshwater Sponge 

 belongs to the vegetable kingdom ; in proof of which, the facts and arguments 



