In response to the observed changes in blood during tail regeneration, a detailed histophysiological study of the haemopoietic organs such as liver, spleen and bone marrow was undertaken. During regeneration, all three organs were found to undergo histophysiological changes. Increased haemopoietic activity in the marrow and hyperplasia of the white pulp were the important changes shown by the bone marrow and spleen respectively. In the liver, the most marked effect appeared to be the formation of large numbers of lymphocytopoietic nodules. Another interesting observation was the influx and destruction of red blood cells both in the liver and spleen, once during the early regressive phase and once during the late progressive phase of regeneration. An attempt is made to correlate these changes in the three haemopoietic organs with the possible involvement of lymphocytes in the formation of a regeneration blastema and a possible haemoglobin transition during regeneration. The present observations are in concordance with the previous observations on blood.