SPONGES OR PORIFERA 



SPONGES are animals. The ordinary bath sponge is only the 

 horny skeleton which in life was encased by living cells. In 

 every living sponge, water is drawn in through numerous small open- 

 ings, and thrown out through large ones. This water passes through 

 the intricate channels of the sponge which are lined with thousands 

 of minute cells, each provided with a collar, and a thread-like lash, 

 which serves to capture and engulf the minute animals and plants 

 that are drawn in with the water. In some sponges the skeleton is 

 calcareous, and is composed of a vast number of curiously shaped 

 spicules. In others it is mainly horny and fibrous as in commercial 

 sponges, while in some, such as the Venus basket of the China 

 Sea, it is glassy. The eggs develop within the sponge itself and 

 are usually cast out as minute spherical or oblong larvte covered 

 with cilia which enable the little creatures to swim rapidly through 

 the water. In a few hours or days, however, they settle to the bot- 

 tom and soon grow into sponges. Sponges of the same species often 

 vary greatly in form, in accordance with the situation in which they 

 grow, and they possess so little individuality that two sponges 

 growing side by side will often fuse into one large mass. Sponges 

 may also be cut into pieces, and each piece Avill grow into a perfect 

 sponge. Good accounts of our American sponges are given by 

 Hyatt, Memoirs of the Boston Society of Natural History, 1875 and 

 1877, and Lambe, Transactions of the Royal Society of Canada, 

 1892-94, 1896, 1900. 



COMMERCIAL SPONGES 



Our commercial sponges are found living only in the warmer 

 seas, such as the waters of Florida, the West Indies, the Red Sea 

 and Mediterranean. The sponges from Florida and the West 

 Indies are inferior to those of the old world. There are many va- 

 rieties of the commercial sponge but they all belong to the genus 

 Spoitgia and have a skeleton made up of tough, closely meshed, horny 



