Select the INCORRECTLY spelt word.

The correct answer is Couragious.

Explanation:

Let's check the spelling of all the given options:

1. Physiologist: Correctly spelt. It refers to a specialist in physiology, the branch of biology that deals with the normal functions of living organisms and their parts.

2. Gracious: Correctly spelt. It means courteous, kind, and pleasant.

3. Contagious: Correctly spelt. It refers to a disease spread from one person or organism to another by direct or indirect contact.

4. Couragious: Incorrectly spelt. The correct spelling is Courageous (which means brave or possessing courage).

Therefore, Couragious is the incorrectly spelt word among the given options.