282 SECRETS OF ANIMAL LIFE 



material. When the animal is living this delicate 

 covering is pliable like chain armor. 



What Mr. Heron-Allen is bold enough to call 

 " intelligence " is even more strikingly exhibited 

 by the effective manner in which some of the shell- 

 builders use their materials. Many years ago 

 Canon Norman described how Technitella (i.e. " the 

 little workman") builds its shell of fragments 

 of minute sponge needles, " laid down in regular 

 Order side by side, and cemented with a mortar 

 composed probably of the finest dust of quartz, so 

 that the whole test is of exquisite snowy whiteness." 

 But the accidental breakage of the shell of a species 

 of Technitella revealed to Mr. Heron- Allen and his 

 sldlful collaborator, Mr. Earland, an even more 

 striking fact. The whole shell-wall consists of two 

 distinct layers of spicules, an outer layer with their 

 long axis parallel to that of the test, and an inner 

 layer at right angles to those outside, " giving as 

 close an approximation to the woof and warp of a 

 textile fabric as is possible with a rigid non-flexible 

 material such as sponge-spicules." When we re- 

 member that this is no matter of " organic crystalliza- 

 tion," but the result of placing extraneous materials, 

 selectively gathered, in a definite and singularly 

 effective arrangement, we feel that we are approach- 

 ing the dawn of art. It is obvious that by the 

 crossing of the two layers of spicules " the strength 

 and resistance of the test to strain is enormously 

 increased." In some cases the use of the spicules 

 is probably protective against the attacks of minute 



