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XXIV. — On Ciliary Action in the Spongiadece. 

 By J. S. Bowerbank, Esq., F.R.S., &c. 



(Read November 13, 1850). 



Although so many years have elapsed since Dr. Grant described 

 the ciliated gemmules of Halichondriapanicea, and demonstrated the 

 existence of continuous currents of water from the great ex-current 

 oscula of more than one species of the same genus ; and although it 

 has grown into an almost universal belief among naturalists, that 

 the currents must be the result of ciliary action ; still the existence 

 of these important organs in the Spongiadece had never been clearly 

 demonstrated, even with all the additional aid afforded by the mo- 

 dern improvements of the microscope. I had long felt this to be an 

 opprobium to naturalists, and had determined, on the first convenient 

 opportunity, to endeavour to solve the problem ; when, in the course 

 of the summer of the present year, I received a letter from my friend 

 Dr. Johnston, of Berwick-on-Tweed, in which he mentioned that Dr. 

 Dobie had succeeded in seeing the cilia in the Spongiadece. Stimu- 

 lated by this information, I determined that in the autumn I would 

 locate myself at Tenby, in South Wales, and follow out the 

 investigation ; and with a view of preparing myself for the work, I 

 requested my friend Dr. Johnston to put me in communication with 

 Dr. Dobie, to whom I wrote on the 13th of September. On the 

 27th of the same month I received a reply, from which the following 

 is an extract : — " In February last I was residing for a short time 

 near Berwick-on-Tweed; and, though quite ignorant of species of 

 sponges, I determined to examine carefully any specimens I could 

 pick up, with reference to the existence of cilia. I found a species 

 of Halichondria very abundant, but, after repeated examinations, 

 failed to discover these organs. In a species of Grantia I was more 

 fortunate, having picked up several individuals in which vigorous 

 currents were in operation. I slit up a specimen, and removed a lit- 

 tle of the gelatinous matter lining the inner surface. This I exa- 

 mined with a ^--inch lens. The field of view was crowded with the 



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