Kinetic properties of aspartate transcarbamylase (ATC) in crude extracts of Artemia were studied. The enzymatic kinetic is linear with respect to time for at least 1 hr with crude extract from cysts or the earliest development stages, but not with crude extract from older stages. ATC activity was assayed during early stages of development of two Artemia strains ; a relation has been sought between ATC activities and growth rates. [NOT CONTROLLED OCR]