Pwm Circuit Schematic

Transistor heats up too much when connected to Dc motor.?

OK here is the picture of my connections, not exactly a schematic because I would probably draw that wrong.

http://i54.tinypic.com/311kwoi.jpg

I am powering the Micro Controller with 5v
The DC motor is rater 9-18v and i am using 12v

The base of the transistors is getting PWM signals to just slowly increase the speed and then back down (0-5volts)
And i have read about connecting grounds together and so i did.
But the transistor gets really really hot? i mean i know they dispense heat but THAT hot? this is like a baby circuit … or are my connections wrong?
alright fellas , yes its the exact same transistor as show in the picture and no other wires are connected other then what is show , and yes i will add a resistor to the base i am in the midst of reading up on that , and I suppose a diode (on backwards) right? so my Arduino does not get fried

Circuits such as this might provide a lot of current and unless limited by an external resistor, the base current may actually be high to result in large dissipation. But having placed a resistor in series with base, and a shunt diode across the motor (THAT IS A MUST), if transistor still heats up, you have to look into the CURRENT that the motor draws. A heat sink in the transistor will help, but that may not be the problem. I guess the transistor should not be dissipating more than 2watts, (VCE of 0.4V and current of say 5 amps), unless the transistor is a darlington type. Is it? What is the type number?? A Darlington can dissipate 0.8 to 1V multiplied by 5 amps if 5 amps is the current.That is a power of 4 to 5 watts.

PWM SCHEMATIC