Sources:
https://www.boundless.com/biology/definition/gastrovascular-cavity/
http://mcb.berkeley.edu/courses/bio1a/downloads/Animal_Phylum_poster.pdf
http://www.biosciweb.net/animal/pdf/chord.pdf
http://eol.org/pages/2195/details#reproduction
http://www.mesa.edu.au/echinoderms/
http://global.oup.com/us/companion.websites/9780195326949/student_resources/facts/
http://thecircleofblood.weebly.com/chordata.html
http://www.ucmp.berkeley.edu/chordata/chordatamm.html
http://mcb.berkeley.edu/courses/bio1a/downloads/Animal_Phylum_poster.pdf
http://www.biosciweb.net/animal/pdf/chord.pdf
http://eol.org/pages/2195/details#reproduction
http://www.mesa.edu.au/echinoderms/
http://global.oup.com/us/companion.websites/9780195326949/student_resources/facts/
http://thecircleofblood.weebly.com/chordata.html
http://www.ucmp.berkeley.edu/chordata/chordatamm.html