148 



BOYS AND GIRLS IN BIOLOGY. 



is called the optic nerve, and it is connected with each 

 square by pretty rods and cones, which look like those 

 in your own eye (Fig. 126). The rods and cones are 

 covered with coloring-matter, or pigment, which turns 

 red when it is boiled. The optic nerve is a nerve of 

 sensation, because it gives the lobster the sense of sight. 

 Now, where are the lobster's ears ? Not in the foot, as 

 the mussel's, but in their proper place — the head. If 



Fig. 12T. 



Little Feelek, or Antennule, showing Ear-Tube at its Base. 



you look at the base of the little feelers on each side, you 

 will find a little three-cornered slit covered with hairs 

 (Fig. 127). This slit leads into a small sac filled with 



