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What are the phylum of cleavage animal?
Complete cleavage mainly includes: radiation cleavage, such as echinoderms and amphioxus; Spiral division, such as some mollusks and polychaetes; Bilateral symmetrical cleavage, such as sea squirt; Irregular cleavage, some eggs are spiral at first, and then become bilateral symmetry, such as some annelids; Some cleavage procedures are irregular, that is, the initial cleavage of blastomeres is not synchronized, resulting in 3- cell phase, such as most mammals. Mammals divide into 16 ~ 64 cell phase and form multicellular solid pellets, which are typical morulae. Incomplete cleavage: Dislike cleavage occurs on the polar blastoderm of animals, and the yolk under the blastoderm does not divide, such as teleost and reptile. Surface cleavage, a large number of yolk of insect eggs are concentrated in the center of the egg, the nucleus and a small amount of cytoplasm are located in the center, and most of the cytoplasm is distributed around the egg. After many divisions, the cleavage ring is finally located on the surface of the egg.