How can you tell the difference between the dorsal side and the ventral side of the earthworm?

The earthworm's mouth has the prostomium front tip of the worm which hangs over. Notice the presence of tiny bristles called setae which are found on the ventral surface of the earthworm. Another dissimilarity between the dorsal and ventral surface is the fact that the ventral surface is lighter in color.

this protocol provides a detailed procedure for chromatin immunoprecipitation (chip) to study the dna-protein interactions.