In this type an organism breaks down into two or more pieces, each of which grows into a new individual. This means of reproduction is found in the organisms -which have good power of regeneration. Sponges and hydroid coelentrates exhibit this type of reproduction. If a sponge is macerated by pressing it through fine gauge, the separated cells come together in groups and grow into new individuals.
Very small fragments of free-living flatworms will regenerate into new individuals if right conditions are provided to them. A nemertine worm, Lineus, develops rings of constriction which cut the body into short fragments. These animals possess large number of undifferentiated cells which, when required can proliferate and develop into any kind of tissue.