Question

what is the fertilisation of annelida and mollusca , cnidaria​

Answer 1

Flatworms (Phylum Platyhelminthes), annelids (Phylum Annelida) and mollusks (Phylum Mollusca), while extraordinarily diverse, share a number of characteristics, which suggests they are more closely related to each other than other invertebrate phyla. Unlike poriferans and cnidarians, all three of these phyla are bilateral and have 3 tissue layers. This means the presence of a head with a concentration of nervous tissues. All of these phyla are also protostomes, or "mouth first" animals.