Pig
Worm
Frog
Starfish
Crayfish
Fish
Mussel
Brain
Yes
No - a collection of nerves in head
Yes
No - do have ring/radial nerves instead
Yes
Yes
No
Skull
Yes

Yes

No - protected by exoskeleton
Yes - fairly thin

Spine
Yes - towards dorsal side

Yes - towards dorsal side

No - Crayfish are invertebrates
Yes - in center

Nerves
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Location of Nerves
In skin and muscle

In skin and muscle
One in each of five legs

In skin and muscle
In muscle
Type of Nervous
System

- Typical Vertebrate Nervous
System
- Two longitudinal Nerve Cords-->
Ventral Nerve cord
-Ganglion in each body segment
- Dorsal Nervous system
- Radial nervous system

- Typical Vertebrate Nervous
System