Define the following terms:
$(i)$ Cocoon
$(ii)$ Worm casting

(N/A) $(i)$ Cocoon: It is a protective structure secreted by the clitellar glands of an earthworm,which stores fertilized egg cells or ova for development.
$(ii)$ Worm casting: In earthworms,the undigested food material that is excreted through the anus in the form of small,granular heaps is known as worm castings.