26 



for the formation of the Silica in a gelatinous state and exhibited 

 a quantity of the "Flint Jelly" which had formed during the 

 evening. 



January 3rd . 



Mr. FaUa^ar exhibited the fresh water sponge (Spongia 

 fluviatilis), illustrated by diagrams, showing (since the last 

 meeting December 6th) the production by gro^vth of the 

 pellucid, semi-transparent, gelatiuoid substance termed sarcode, 

 which had extended to some distance on the glass cell in which 

 it was placed ; in the new sarcode the pores tlu-ough which the 

 current of water enters the sponge were observable, forming the 

 incurrent, bearing with it the nutriment on which the sponge 

 feeds. In the newly formed sarcode was to be seen a quantity 

 of new spicules ; they were pointed at each end. and their 

 middle or centre was bulged out from which the growth extended 

 to both terminal points ; the mature spicules are a little bent or 

 curved and pointed at both ends, but not bulged out in the 

 middle. Some good specimens of the mature spicules had been 

 cleaned and mounted by Mr. Hammond. They are composed of 

 the pure silex as transparent as glass. The peculiar spicules of 

 the ovaria were beautifully shown under Colonel Horsley's 

 microscope. In a specimen that Mr. Fullagar had successfully 

 mounted in damar, by first dr3-ing the ovaria and then in a drop 

 of damar with a thin glass cover gently pressed down, the 

 granular contents of the ovaria were pressed out, and the 

 beautiful stellated form of the spicule was seen standing out in 

 form of so many miniature palm trees ; the real foi-m of them is 

 stellated, at the two ends, connected together by a shaft, similar 

 to two wheels on an axle. This form of spicule in the ovaria 

 performs the double office of tension and defence. 



In thanking Mr. Fullagar for his interesting observations and 

 excellent drawings of the Fresh-water Sponge, Mr. Dowker 

 observed that Mr^ Fullagar had very aptly chosen the sponge 

 for his observations, after having studied the Amoeba and 

 Actinophrys, as they possessed many properties in common. 

 The sponge at one "time had been considered a vegetable, but, 

 though low in the scale of the animal world, it was endowed 

 with many of the organs of the higher animals. The observa- 

 tions of Dr. Bowerbank and Mr. Grant had thrown a flood of 

 light on these interesting animals. Mr. Fullagar has been 

 happy also in getting tlie sponge to live and grow in confine- 

 ment. The incurrent canals are doubtless clothed A^ith vibratile 

 cilia ; for though these are very difilcult of detection, owing to 

 their extreme minuteness and transparency, they have been 



