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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.

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The influence of two different seasons as well as of thyroid hormone on tail regeneration in Mabuya carinata has been evaluated by measuring the rate of growth of the regenerate at various time intervals. The analysis has revealed no apparent seasonal alteration in the final length attained at the end of 60 days. However, the average per day rate of growth indicates some difference between the late non-breeding and the early breeding phases. A better growth rate was noticeable in the non-breeding phase during the first 25 days (blastemic and differentiation phases) while it was better in the early breeding phase during the last 20 days of tail regeneration (late differentiation and growth phases). These observations correlate with the differential physiological and endocrine status characteristic of the two seasons. Hypothyroidic animals showed a 71% retardation of regenerative ability as compared to euthyroidic animals, which was however rectified by thyroxine replacement. Modes of action of thyroxine on lizard tail regeneration are discussed.