How does gaseous exchange take place in earthworms , fish?
Earthworm: The earthworm inhabits burrows in damp soil and emerges to feed in the darkness. Gaseous exchange occurs through its skin. The thin, moist skin is supplied with a network of capillaries which absorb oxygen from the atmosphere and deliver it to the rest of the body. The absorbing surface or the network of capillaries also gets rid of carbon dioxide from the body.
Fish: Fish absorbs dissolved oxygen from the water by means of gills. Gills are projection of the skin. These are well supplied with blood vessels for exchange of gases.