314 



NATURAL HISTORY. 



up through the fluid, I soon perceived that there was some intestine motion in the opaque 

 particles floating through the water. On moving the watch-glass, so as to bring one of the 

 apertures on the side of the Sponge fully into view, I beheld, for the first time, the splendid 

 spectacle of this living fountain vomiting forth from a circular cavity an impetuous torrent of 

 liquid matter, and hurling along, in rapid succession, opaque masses, which it strewed every- 

 where around. The beauty and novelty of such a scene in the animal kingdom long arrested my 

 attention ; but, after twenty-five minutes of constant observation, I was obliged to withdraw my 

 eye. from fatigue, without having seen the torrent for one instant change its direction, or diminish, 

 in the slightest degree, the rapidity of its course. I continued to watch the same orifice, at short 

 intervals, for five hours, sometimes observing it for a quarter of an hour at a time, but still the 

 stream rolled on with a constant and equal velocity. About the end of this time, however, I 



observed the current become perceptibly languid, the 

 opaque flocculi of feculent matter, which were thrown 

 out with so much impetuosity at the beginning, were now 

 propelled to a shorter distance from the orifice, and fell to 



the bottom of the fluid 

 within the sphere of 

 vision; and, in one hour 

 more, the current had en- 

 tirely ceased. '' 



Grant afterwards ob- 

 served the currents of 

 water entering the pores, 

 and illustrated his obser- 

 vations by a drawing, of 

 which Fig. 3 is a fac- 

 simile copy. He then 

 sought for the cause of 

 the water-streaming, and 

 lightly conjectured that it 

 must be due to ciliary 

 action, but sharp-sighted as 

 he was he failed to find the cilia, though he especially looked for them. They were subsequently 

 discovered, however, by Dobie, Bowerbank, and Carter, and the last showed that the cells bearing 

 the cilia, or flagella, as these whip-like filaments are termed when each cell bears only one of them, 

 are usually arranged in spherical chambers, to which he gave the name of ampullaceous sacs, but 

 which are now more generally known as flagellated chambers. Finally, F. E. Schulze, in his faithful 

 and beautiful illustrations of Sponge-structure, showed exactly how these flagellated chambers are 

 brought into relation with the excurrent and incurrent canals ; and this brings us back to the 

 Bath Sponge. In this, as in most other Sponges, the terminal branches of th? excurrent canals dilate 

 at their ends into flagellated chambers (Fig. 4, c), about O001 inch in diameter, which are clustered 

 about the penultimate branches of the excurrent canals like grapes in a bunch. The terminal 

 branches of the incurrent canals apply themselves to the round ends of the chambers and open into 

 them by one or usually more small circular pores. The flagellated cells are arranged in a single 

 layer on the walls of the chamber, and rapidly lashing the water in one direction drive it into 

 the excurrent canals ; the multitudinous little streams so produced flow together in the larger 

 excurrent tubes, and are finally discharged in a powerful current through the oscules. The water 

 driven out of the chambers is replaced by an inflow from the incurrent tubes, and the loss from these 

 is made good by the minute currents which stream through the dermal pores. These entering currents 

 bear with them minute protelnaceous particles, such as minute infusoria, diatoms, and minute algae ; 

 they also contain oxygen in solution ; the outflowing currents carry away faecal residues, and also 

 the excreta urea and carbonic acid. The solid particles of food are ingested by the cells lining 

 the excurrent canals, and particularly by the flagellated cells. This can most readily be proved by 



Fig. 2. POHIFEHOUS SURFACE OF A SPONGE (Sfowjelia avara. After Schuhe.) 

 A, Magnified 10 diameters ; B, a single mesh, x 60 diameters. 



