An adult <i><a href="https://en.wikipedia.org/wiki/Ascaris_lumbricoides" class="extiw" title="wikipedia:Ascaris lumbricoides">Ascaris lumbricoides</a></i> worm.  Diagnostic characteristics: tapered ends; length 15 to 35 cm (the females tend to be the larger ones).  This worm is a female, as evidenced by the size and genital girdle (the dark circular groove at bottom area of image).
<p>CDC Division of Parasitic Diseases
</p>
<ul><li><a rel="nofollow" class="external free" href="https://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Ascariasis_il.htm">http://www.dpd.cdc.gov/dpdx/HTML/ImageLibrary/Ascariasis_il.htm</a></li>
<li><a rel="nofollow" class="external free" href="https://www.dpd.cdc.gov/dpdx/images/ParasiteImages/A-F/Ascariasis/Ascaris_female.jpg">http://www.dpd.cdc.gov/dpdx/images/ParasiteImages/A-F/Ascariasis/Ascaris_female.jpg</a></li>
<li>Originally uploaded to <a href="https://en.wikipedia.org/wiki/wikipedia" class="extiw" title="en:wikipedia">en:wikipedia</a></li></ul>