THE SPONGES 31 



and, on reflecting the light of a candle 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 spec- 

 tacle 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 everywhere 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 con- 

 stant and equal velocity. About the end of this time, however, 

 I observed the current become perceptibly languid ; the opaque 

 flocculi of faeculent 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 entirely 

 ceased." Although Grant suspected that these currents were 

 due to the movement of cilia, he failed to detect them, and they 

 were subsequently observed by other workers. 



That we may gain some idea of the main characteristics of the 

 Sponges, we will first examine a small, simple Sponge which is 

 to be found attached to the rocks in deep pools on the shore at 

 low-tide mark. This is the little Sycon Sponge (Sycon gelatinosum), 

 which grows as a tuft of short, branching cylinders, about 2 or 

 3 inches long, all connected together at the base where the Sponge 

 is attached to the rock. In its simplest form the body of a Sponge 

 is shaped like a cylinder or vase, attached to a base at its closed 

 end, and with the upper, free end open ; so that Sycon may be 

 likened to several of these single cylinders joined together at their 

 base. If a portion of the Sycon Sponge be examined under the 

 microscope, it will be seen that there are groups of minute open- 

 ings the inhalent pores pretty evenly distributed over the outer 

 surface, and that the free end of each branch or cylinder has a 



