Pila is an amphibian. It shows many sense organs.
It is leaf like. It is 6 to 7 mm. in length. It isbipectinate. It bears a median axis. From this axis 22-28 lamellae will arise in two rows. This structure is innervated by a nerve coming from left pleural ganglion.
This will test the purity of water.
2) Eye : On the head of Pila two stalks are present. They are called
ommatophores.They bear eyes. Each eye is black and round.
In the section of the eye a central sac like structure is present. It is called optic vesicle Eye is derived from ectoderm. Optic nerve is connected to the eye.
In the sac of the eye a lens is present. The inner surface of the sac shows retina. In this retina visual cells and supporting cells are present.
This eye of Pila cannot form image of the object.
3) Statocyst :
On either side of the Pedal ganglion two statocysts are present. Each statocyst is pear shaped. Each statocyst is hollow bag like structure.
It is covered by connective tissue. It is derived from ectoderm'.
In the sac of this statocyst watery fluid is present. In this fluid calcareous particles are present called statoconia.
This is connected with a nerve coming from Pedal ganglion. This will maintain equilibrium.
4) Tentacles :
On the head of Pila two tentac'es are present.
1) The first pair of tentacles are called cephalic tentacles.
2) The second pair of tentacles are t.ue tentacles. They are tactile sense organs.