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XXI. Observations on the Spongilla fliiviatilis. In a Letter to the Secretari/. 

 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 yoii with some specimens of the River 

 Sponge {Spongilla Jluviat'iUs), 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 Spongiu JluviatiU^, Linn, and 

 Palla.s, Spongilla friabilis (De Lamarck), Ephydatia Jiaviatilis (Lamouroux), 

 Titpha Jluviatilis (Oken), and HuUcJiondria Jliiviatilis (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 Iiint 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. 



