They have an internal digestive chamber, with one or two openings; the gametes are produced in multicellular sex organs, and the zygotes include a blastula stage in their embryonic development.
ðeɪ hæv ɐn ɪntˈɜːnəl daɪdʒˈɛstɪv tʃˈeɪmbɚ, wɪð wˈʌn ɔːɹ tˈuː ˈoʊpənɪŋz; ðə ɡˈæmiːts ɑːɹ pɹədˈuːst ɪn mˌʌltɪsˈɛljʊlɚ sˈɛks ˈɔːɹɡənz, ænd ðə zˈaɪɡoʊts ɪŋklˈuːd ɐ blˈæstʃələ stˈeɪdʒ ɪn ðɛɹ ˌɛmbɹɪˈɑːnɪk dɪvˈɛləpmənt.