THE SIMPLEST ANIMALS 1 7 



tint. At some oyster stations it is common to grow the 

 oysters on wire frames which can be raised at intervals 

 and exposed to a shower of rain. The fresh water kills 

 the sponge, but the oyster by closely shutting its shell 

 remains unscathed. To this group belong the vivid 

 green fresh-water sponges. 



The Bathsponges with their skeletons of horny yellowish 

 substance, and the highly-organised industry to which 

 they have given rise, deserve special mention. Three 

 main species are fished in the Mediterranean ; the most 

 important fisheries have long been established in Florida, 

 the Aegean Sea and North Africa. These sponges, so 

 attractive in their commercial form, are black and slimey 

 during life and are securely anchored to shells, rocks or 

 other solid objects. Up-to-date diving apparatus is often 

 used to gather them, but much of the work is still done 

 by naked native divers, whose methods of operation 

 vary with the locality. The native divers of the Aegean 

 are world-famous for their skill and endurance. The 

 diver has a life-line attached to his right arm and thus 

 equipped leaps overside with a 30 lb. block of marble, 

 which bears him to the sea-bed 12 to 40 fathoms below. 

 Here he stays for about two minutes, filling a basket 

 with sponges at lightning speed, when he is hauled to 

 the surface, his marble " sinker " attached to another line 

 being recovered separately. The sponges are stamped 

 upon and beaten and then hung overside for twenty-four 

 hours in order to remove the last of the slimey substance. 

 There follows more beating, many washings, and finally a 

 period of drying in the hot sun, the sponges being hung 

 on lines. In some areas bathsponges are propagated by 



