Yolk and copper utilisation during embryogenesis of the fresh-water prawnCaridina nilotica var.bengalensis (De Man) have been described. The egg number/brood increased with increase in length as well as volume (L8) of the mother animal. The water content increased from 61·3% (I stage) to 76·4% (III stage) as development proceeded. Fat appeared to be the major source of energy for embryonic metabolism. During development 28·4µg of dry substance were utilised for embryonic metabolism. The pattern of copper absorption followed the trend of salt absorption.