The Relation of the form of a Sponge 

 to its Currents. 



By 

 G. P. Bidder, ScD.^ 



With 12 Text-figures. 



All zoologists know that from the large holes, which we call 

 oscula, on a sponge, an outgoing current may be detected 

 in life. During several months in Naples I investigated this 

 current, using litmus and carmine solutions, and carmine and 

 indigo in suspension. I worked with two calcareous species of 

 sponges, having oscula at the end of tubular prolongations, 

 which reach the size and shape of a child's thumb in the case 

 of Leucaltis, and of a child's finger in the case of 

 Leucandra aspera (Text-fig. 1). The solutions were either 

 placed on the surface of the sponge, to be sucked in by its 

 currents (Text-fig. 2), or dropped by a pipette through an 

 incision into the cloaca — the cavity of the tubular prolongation. 

 In the latter case the time taken for the colour to be thrown 

 out at the osculum, though liable to many corrections, afforded 

 on the whole the most trustworthy determinations of oscular 

 velocity : the cloaca being wider than the osculum, the observed 



^ This paper was read before the British Association at Hull, September 

 1922. A preliminary note was published in ' Proc. Camb. Phil. Soc.', 

 1888, vol. vi, p. 5. (See also ' Quart. Journ. Micr. Sci.', vol. .38, p. 28 ; 

 ' Proc. Roy. Soc.', vol. 64, p. 61 ; and I. B. J. Sollas, ' Camb. Nat. Hist.', 

 vol. i, p. 235.) The experiments were made in the Naples Zoological 

 Station m 1887, 1888, and 1889, where I occupied the Cambridge University 

 table, and in 1890, 1891, and 1892 at a table allowed me by the great 

 kindness of the late Professor Anton Dohrn. For a long time I proposed 

 to myself to make a further series of experiments to clear up doubtful 

 points, but recognizing that I shall not now do so, I have reconsidered 

 all the experiments this year (1922) and recalculated all results and formulae. 



