Modify Individual will take you to a new dialog in which an individual's genotype may be modified directly and its fitness changed. Changes you make to the individual will show up in your Maya scene so you can see what you are doing. If you want to make fine adjustments to a design before evolution continues, select this. If you want the changes you make to have a chance of surviving in future generations, be sure to give your modified design a low unfitness to give it a better chance of having many offspring.
Click on any region in the image to the right to find out more about what it means.