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XXI. Observations on the Spongilla fluviatilis. In a Letter to the Secretary/. 

 By John Hogg, Esq., M.A. F.R.S. L.S. ^ C.P.S. 



Read June 5th, 1838. 



X HAVE taken the liberty of troubling you with some specimens of the River 

 Sponge {Spongilla fluviatilis), for the purpose of calling the attention of the 

 members of the Linnean Society to this curious substance, and more particu- 

 larly to the seedlike bodies which are so abundantly contained in one of them. 



This species of Sponge is synonymous with Spongia fluviatilis, Linn, and 

 Pallas, Spongilla friahilis (De Lamarck), Ephydatia fluviatilis (Lamouroux), 

 Tupha fluviatilis (Oken), and Halichondria fluviatilis (Fleming); and was 

 taken by me last August from a rivulet at Norton in the county of Durham. 



You will perhaps be surprised that I should even hint at, much less ex- 

 press any doubts respecting the animal nature of the Freshwater Sponge ; for 

 modern naturalists have long been almost unanimous in assigning to it a 

 station in the class Zoophytes, and in which are likewise included the Ma- 

 rine Sponges. But I must mention that Dr. George Johnston, who is both 

 an excellent zoologist and botanist, has decided upon restoring the Sponges 

 to the place they formerly occupied in the vegetable kingdom ; and I will 

 merely refer you to his reasons for this decision in his " History of British 

 Zoophytes," given in the first volume of the " Magazine of Zoology and Bo- 

 tany," at pages 229 and 230. Hence it appears that there still exists amongst 

 authors some uncertainty concerning their true nature*. Now, my chief 

 object in exhibiting these specimens of Spongilla is to endeavour to excite 

 some naturalist to make attentive observations on this singular production, 



* See likewise a paper " On the Situation and Rank of Sponges in the Scale of Nature," &c., by 

 Mr. J. E. Gray, contained in the Zoological Journal, vol. i. p. 46.; and Mr. Bell's " Remarks on the 

 Animal Nature of Sponges," at p. 202 of the same volume, published in 1824. 



