Volvox
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Volvox aureus
Volvox is a colonial green algae. The cells are arranged in a gelatinous sphere with two flagella directed to the outside. They divide asexually to produce a daughter colony. Some cells are specialized to produce sperm and eggs for sexual reproduction. Specialization of cells as seen in the reproductive cells is a characteristic of multicellular organisms. Volvox is considered to be a colony because it appears to be intermediate between a group of individual cells and a multicellular organism. Volvox is found in ponds and ditches, and even in shallow rain puddles. Volvox are readily available from science supply companies.