WATER CURRENTS PRODUCED BY SPONGES 445 



of Stylotella. Notwithstanding this general lowness of pressure 

 one of these species, Spinosella sororia, the common Bermuda 

 finger-sponge, produces in the shallow sea a conspicuous deforma- 

 tion of the natural surface of the water, and this deformation can 

 also be observed in specimens that have been transported to the 

 laboratory. As Spinosella was a very satisfactory species to 

 work with, a determination of the volume of water that passed 

 through a single finger of this sponge was attempted. This was 

 made by sinking the tube that had been fastened into the osculum 

 of a finger of Spinosella under the surface of the seawater and thus 

 allowing the water driven by the sponge to escape. The escaping 

 current deformed the surface of the water in the bucket in much 

 the same way as is often seen over a vigorous sponge finger in its 

 natural position in the sea. The rate of the flow of water from the 

 finger was then determined by measuring the velocity of floating 

 particles, such as carmine and so forth, that were carried up the 

 tube by the water current. This proved to be very close to 20 

 mm. in five seconds. As the diameter of the tube was 17 mm. the 

 finger must have discharged a little over 4.5 cc. of water in five 

 seconds. At this rate the discharge would amount to some 78 

 liters a day. This finger measured about 10 cm. in length and 

 averaged 4 cm. in diameter; its osculum had a diameter of about 

 2 cm. Spinosella colonies often consist of as many as twenty 

 such fingers and, assuming that all the fingers work at the same 

 rate as the one upon which the measurements were made, such a 

 colony as a whole would strain in a day about 1575 liters of sea- 

 water or over 415 gallons. 



Since all the measurements recorded in the table were made 

 upon sponges that had been removed from their natural attach- 

 ments and transported to the laboratory and since the effect of 

 such treatment is known to retard rather than accelerate the cur- 

 rents, the results therein recorded are believed to be below rather 

 than above the actual working capacity of the several sponges. 

 This opinion is borne out by an observation made on Spirastrella 

 for which I am indebted to Mr. W. J. Crozier and Mr. D. H. 

 Wenrich. A specimen of this sponge was found partly exposed at 

 low water. Although the osculum was out of water, there was 



