Answer
The graph of the Julia set must be symmetric with respect to the $x-axis$.
Work Step by Step
For $z = a + bi$, the conjugate of $z$ is $\bar{z} = a - bi$
Since $z$ and $\bar{z}$ are symmetric with respect to the $x-axis$, and both $z$ and $\bar{z}$ are in the Julia set as well (proved in 8.2 Ex. 64c), therefore, the graph of the Julia set must be symmetric with respect to the $x-axis$ too.
