TRACHEA, 41 
the body is soft ; some species have only 
six feet placed on the rings next the head, 
and two formed of a hollow membrane, 
which are placed on the last ring. 
Lucy, What is the meaning of mem- 
brane, mamma? 
Mother. It is a sort of skinny sub- 
stance, which is so elastic as to have the 
power of contracting or closing up, and 
of expanding or stretching out. These two 
membranous feet slope backwards ; they 
are hollow, and the part on which they 
w^alk is formed of a shelly ring, and 
fringed with very short hair. Those 
caterpillars, for instance, which I told 
you resembled little twigs, have no more 
feet than these, that is, six horny feet for 
walking with, and two membranous 
feet on the last ring; but the greater 
number have eight more feet, all of the 
membranous kind, and placed four on 
each side. Through these ten mem- 
branous feet the caterpillar breathes ; and 
they are called trachea, a Greek word, 
which signifies a windpipe. 
