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 
skilful 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 
