FOSSIL SPONGES, ETC. ^ 



As the reader may see by referring to Mr. Saville 

 Kent's splendid work on " Infusoria," this sponge- 

 flesh is frequently almost made up of collared in- 



Fig. i. Spicules of Recent Sponge (Chalina). 



fusorians, in company with myriads of still more 

 simple organisms resembling Amoeba. A living 

 sponge, therefore, may be regarded as a colony of 

 lowly organized animals, just as a mass of living reef- 

 coral is a colony of sea-anemone-like animals. 



Let us carry this illustration a little further. The 

 coral-anemones differ from our well-known sea- 

 anemones by the hard limy substances in their 

 interiors, due to the calcification of the tissues. These 

 remain behind after death, and when the flesh has 



