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centrolecithal ovum[¦sen·tro′les·ə·thəl ′ō·vəm]
a female reproductive cell, or ovum, whose cytoplasm contains a large quantity of centrally located yolk. Cytoplasm containing no yolk is found mainly on the surface of the ovum; only a small portion of cytoplasm occurs in the center of the ovum, where the nucleus is located. The central portion of the cytoplasm is connected to the peripheral layer of cytoplasm by delicate strands that pass through the yolk layer. Centrolecithal ova are characteristic of many arthropods, in particular, insects. When a centrolecithal ovum undergoes cleavage, the nucleus divides many times. The resulting nuclei migrate along the cytoplasmatic strands to the surface of the ovum, where cells form around them. This cleavage is called superficial.