Solution

Gametic Exchange in Earthworm : Earthworms are hermaphrodite animals; which means an individual has both the sexes. A pair of male genital pore is present on the ventrolateral side of the 18th segment. Four pairs of spermathecae are located in the 6th to 9th segment (one pair in each segment). During copulation. spermatozoa get deposited in the spermatheca. An earthworm needs to find another earthworm for mating. They juxtapose each other so that the male genital pores of one individual are opposite to the spermatheca of another individual. Thus, a mutual exchange of spermatozoa takes place between the two individuals. Spermatozoa are exchanged in the form of packets: called spermatophores. After that, mature egg cells and sperms are deposited in cocoons. Cocoons are made by the fluids secreted by gland cells of clitellum. Cocoons are deposited in soil and fertilization and development of the embryo takes place inside the cocoons.