Members App Logging the user out on page change

Hey Perch Community,

I have a simple login page with the following code:

<perch:member logged-in="true"> 

    <p class="light green">Hi <perch:member id="first_name" />, you are logged in</p>
    <a href="#" class="bold grey">A Link</a>
    <a href="#" class="bold grey">Another Link</a>

<!-- Perch Form Goes Here -->

</perch:member>

The login works great and displays the content under

logged-in="true"

My question is...

Why is it, that after a user is logged in. Upon visiting another page, the user is automatically logged out?

Is there a PHP script that I need to include on other pages to keep the user logged in?

I'm using the following to detect:

<?php 
    if (perch_member_logged_in()) {
        echo '<li class="bold location">Welcome back, '.perch_member_get('first_name').'!</li>';
    }else{
        echo '<p class="light grey">You are not logged in. Please <a href="index.php">Login</a>.</p>';
    }
?>