The formation of erythrocytes in foetus takes place in

The correct option is "liver and spleen".

Here is the step-by-step explanation of why this option is correct:

1. Understanding Erythropoiesis: Erythropoiesis is the physiological process by which red blood cells (erythrocytes) are produced. The site of erythropoiesis changes significantly during different stages of human development (embryonic, fetal, and post-natal life).

2. Early Embryonic Stage: In the first few weeks of embryonic development, erythropoiesis begins in the yolk sac.

3. Fetal Stage (Foetus): As the fetus develops (specifically from the second to the fifth month of gestation), the primary sites of erythrocyte formation shift. During this middle stage of prenatal development, the liver becomes the main site of erythropoiesis, assisted significantly by the spleen.

4. Post-natal and Adult Stage: Towards the end of gestation (around the seventh month) and continuing after birth throughout adult life, the primary site of red blood cell production shifts to the red bone marrow.

Therefore, during the fetal stage, the formation of erythrocytes takes place predominantly in the liver and spleen.