Zoo Mom Science... 

Worm Dissection Photos

Dissecting an earthworm is not difficult, but the pictures in the NASCO booklet can look very different from the specimen in front of you.  This is a brief photographic guide designed to match the preserved specimen.  It does not replace the booklet; it only provides photos as opposed to illustrations.  You will still need to follow the instructions in the booklet.  Due to the quantity of photos, it may take a long time to load.  Another helpful link is http://biog-101-104.bio.cornell.edu/BIOG101_104/tutorials/animals/earthworm.html

Young students may need help with this particular dissection.  Although it is a simple procedure, the long, slender specimen requires fine motor skills to handle and cut.

I find the best way to cut the worm is pin the mouth (anterior end) near the edge of the plate, and hold the worm while cutting.  Pinch the skin slightly and make an incision on the the septum between segments.  then insert the scissor tip and cut slightly off center up towards the clitellum, stopping about 1/2" from the clitellum.

It is not necessary to use a scalpel to separate to septa, your fingers can gently pull the skin open.

Once the worm is open at the clitellum, it can be pinned, and then carefully cut through the clittelum, all the way to the mouth.

LABELLED PICTURE