392 



THE MICROSCOPE. 



attaining more than two inches in thickness. From the 

 other sponges it is distinguished by the smooth spicula 

 which surround its seed-like bodies, and the matted 

 structure. 



Spongilla alba. Its texture is coarse and open ; struc- 

 ture reticulated. The investing membrane abounds in 

 minute spicula; has seed-like spheroidal bodies about 

 l-30th of an inch in diameter, with rough points exter- 

 nally. The large spicula are slightly curved, smooth, 

 pointed at each end, about l-54th of an inch in length ; 

 the small spicula are slightly curved, thickly spiniferous, 

 or pointed at both ends; the former, pertaining to the 

 seed-like bodies, are about 1 -200th of an inch in length ; 

 the latter, pertaining to the investing membrane, are more 

 slender, and a little less in length; these last numerous 

 small fcpiniferous spicula when dry present a white- lace 

 appearance, from which Mr. Carter gives them the name 

 of alba. 



Spongilla meyeni is massive, having large lobes, mam- 

 millary eminences, or pyramidal, compressed, obtuse, or 

 sharp-pointed projections, of an inch or more in height ; 

 also low wavy ridges. Its seed-like bodies are spheroidal, 

 about l-47th of an inch in diameter, studded with little 

 toothed discs. 



Mr. Carter enters very minutely into the structure of 

 " fresh- water sponge, which " he believes " is composed 

 of a fleshy mass, supported on a fibrous, reticulated, horny 

 skeleton. The fleshy mass containing a great number 

 of seed-like bodies in all stages of development, and 

 the horny skeleton permeated throughout with siliceous 

 spicula. When the fleshy mass is examined by the aid of 

 the microscope, it is found to be composed of a number of 

 cells, imbedded in and held together by an intercellular 

 substance. 



" In the development of the sponge-cell of Spongilla, a 

 set of large granules make their appearance at a very early 

 period, and increase in number and size until they form 

 a remarkable feature. At this time they are about 

 1-1 0,000th of an inch in diameter, of an elliptical shape, 

 and of a light amber colour by transmitted light ; they 

 are the colour bearing granules or cells, arid give the 



