Hæm`a*to*gen"e*sis (hĕm`ȧ*t?*jĕn"ē*sĭs or hē`mȧ*t?-), n. [Hæmato- + genesis.] (Physiol.) (a) The origin and development of blood. (b) The transformation of venous into arterial blood by respiration; hematosis.