356 TOILERS IN THE SEA. 



oval or irregular as often as it is circular. These last 

 facts, together with that of the great variability in 

 the calibre of the canals, leaves no doubt in my mind 

 that it is the animal of the sponge which does the 

 boring, and not marine worms, which have politely 

 abandoned their burrows for the accommodation of 

 this toiler in the sea." l 



Dr. O. Schmidt, who may be supposed to have 

 had a rather intimate knowledge of sponges and 

 their habits, observes that "a large portion of the 

 coasts of the Mediterranean and Adriatic Seas is 

 composed of calcareous material, which, from its 

 tendency to become eroded, has a broken, jagged 

 aspect, giving it a peculiar and often attractive 

 appearance. Of such broken coast, one can certainly 

 measure off some thousands of miles of strand, and, 

 where it does not descend too abruptly, large and 

 small stones and fragments of rocks cover the ground. 

 One can scarcely pick up one of these billions of 

 stones, without finding it more or less perforated with 

 holes, and eroded by Cliona (burrowing sponge), often 

 to such a degree that the spongy remains of the 

 apparently solid stone may be crushed by the hand." 



Again, Dr. Leidy remarks that " an extensive bed 

 of oysters, which had been planted at Great Egg 



1 "Destructive Nature of the Boring Sponge," by J. A. 

 Ryder, in "American Naturalist," vol. xiii. (1879), p. 279. 



