374 MANUAL OF NATUEAL HISTORY. 



6. Family. — Pelagic-Foraminifers (Thalassicollidse). 

 Shell, when present, transparent, brittle, 

 either perforated by numerous rounded aper- 

 tures, or with the apertures prolonged into 

 short tubes. 



SPONGES. 



The Sponges, although they have been claimed as 

 the property both of the Phytologist and Zoologist 

 respectively, are, at present, usually regarded as 

 members of the Animal Kingdom, though their claims 

 to this distinction are certainly not very obvious. 

 No indication of sensation has been detected in their 

 amorphous bodies : in fact they cannot be said to 

 feel as much as many undoubted vegetables. They 

 have no stomach or receptacle for food, usually re- 

 garded as the "sine qua non" of an animal, for their 

 substance is permeated by canals, which convey the 

 water, in which their nourishment is dissolved, to 

 every part. The Sponges, however, differ from plants, 

 in giving out, when burned, a smell resembling burnt 

 horn, which indicates the presence, in considerable 

 abundance, of nitrogen in their composition. Their 

 more animal part is a thin, transparent, gelatinous 

 layer which invests the complicated tissue of horny 

 fibres usually known under the name of " Sponge," 

 but which is in reality the skeleton of these animals. 

 The Sponges of commerce are obtained in considerable 

 quantities from the Mediterranean, and are usually 



