I'm pretty sure your talking about Vertebrates
A prothallium, or prothallus<span> is usually the </span>gametophyte<span> stage in the life of a </span>fern<span> or other pteridophyte. Occasionally the term is also used to describe the young </span>gametophyte<span> of a liverwort or peat moss as well.</span>
D because all the other answer are negative feedback
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