Flowerlike Forms and Fantasies 169 



tion of cells, they have not so far progressed as to 

 acquire a stomach or anything resembling the special- 

 ized organs that distinguish other multicellular crea- 

 tures. It is on account of their low organization that 

 they may be cut into pieces without killing the indi- 

 vidual, for each piece will continue to live and grow; 

 by the same token, certain members of the same species 

 are enabled to coalesce when coming into contact. 



As all animals must eat in order to live and grow, 

 the individual sponge, notwithstanding its having no 

 mouth or stomach, manages this important business 

 In a very efficient way. And although utterly inca- 

 pable of locomotion, it captures its food in a manner 

 no less adroit than that of the most active swimmer. 

 To arrive at an understanding of how this Is done, let 

 us look more closely into its structure. 



In the living animal, the organic parts — that Is, those 

 parts which do not comprise the framework — are made 

 up of a soft jellylike tissue consisting of three different 

 layers of cells. The outside layer, which Is virtually 

 the skin, Is composed of flat cells, and is called the 

 ectoderm. The middle layer, known as the mesoderm, 

 makes up the main mass of the body, and It Is the 

 function of these cells, which are of various shapes 

 and kinds, to form the framework and take part In the 

 reproduction and digestion. The internal layer, or 

 endoderm, Is an arrangement of cylindrical cells, each 

 one of which has at Its exposed end a cup, or collar, that 

 encircles the base of a freely lashing flagellate hair. 

 Now these thread cells {choanocytes) , so-called, liter- 

 ally line the walls of the many locks, or chambers. In 

 the canal system that traverses the sponge, and it Is they 



