What is a group of acalephs, including the naked-eyed medusæ; the hydromedusæ. Most of them are known to be the free-swimming progeny (gonophores) of hydroids called?

gymnophthalmata — A group of acalephs, including the naked-eyed medusæ; the hydromedusæ. Most of them are known to be the free-swimming progeny (gonophores) of hydroids. (Webster's 1913.)

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