126 



FIRST LESSONS IN ZOOLOGY 



ma}' be over a meter (39 in.) in height. In color they 

 may be red, purple, orantje, gray, and sometimes blue. 

 Examine a batli sponge and note the holes in it. 



These are to let in and out the 

 sea-water, in which float the 

 minute bits of animal or plant 

 substance on which the sponge 

 feeds. This water also brings 

 o.xygen for the breathing of 

 the sponge, and carries away 

 the carbon dioxide given off 

 by it. But the sponge has no 

 special organs, its soft flesh 

 being able to digest food and 

 take up oxygen without stom- 

 ach or lungs. 



The living sponges are col- 

 lected by divers, or are dragged 

 up b)- men in boats with long- 

 poled hooks or dredges. 



They are first killed by ex- 

 posure to the air, and then 

 thrown into tanks of water. 

 Here the flesh decays away, 

 leaving the tough, horn)', or 

 ,, „ ,,,, , , ^ leathery skeleton, which, 



I-k;. 87.— 1 lit- bkeletnri of a ■' 



" glass " sponge (skeleton com- when cleaned, bleached, and 



loosed of siliccrms spicules) from . -.„ i ■ j r i i. 



J:,pan. (Natural size; fmm trimmed, IS ready for market. 



spi.-cimen.) Some sponges have a lime and 



some a glass skeleton instead of a horny one, and the 

 glass slv'elctons are often very beautiful (see fig. '$>'/). All 

 the sponges compose the animal branch called Poi-ifcra. 

 Sea-anemones and corals. — The sea-anemones which 

 are common in tide-pools, ami the coral animals ^\'hich 

 live in tropic and sub-tropic oceans, ha\'e the same type 



