Early bipinnaria larva

The early bipinnaria larva of an echinoderm is little more than a modified gastrula.  Using the high magnification image, notice that the blastopore has become the anus and a new opening, the mouth, has appeared in the body wall and becomes continuous with the archenteron to complete the digestive tract. 

Late bipinnaria larva

Observe the late binnaria larva on display. In this older larva the digestive tract and bands of cilia are well developed (but not visible in these images). Note that the larva is still bilaterally symmetrical. In later stages of development (which we will not study) the larva will secondarily become radially (or pentaradially) symmetrical.  The high magnification image is labeled.