A PHYLOGENETICAL SURVEY OF HEMOCYTOPOIETIC TISSUES IN SUBMAMMALIAN VERTEBRATES : WITH SPECIAL REFERENCE TO THE DIFFERENTIATION OF THE LYMPHOCYTE AND LYMPHOID TISSUE

A phylogenetical survey of hemocytopoietis tissues was made of tue submammalian vertebrate series from cyclostomes up to birds, with special emphasis on the differentiation of the lymphocyte and lymphoid tissius. The chief results obtained are as follows: 1.At the level of cyclostomes, only granulocytopoieric tissus is differentiated in the spriak valve of intestine which corresponds to spleen of higher vertebrates. Neither eryhrocytopoietic nor lymphocytopoietic tissue is found anywhere at this level. 2.At the succeeding level, represented by the elasmobranchs, both granulocytopoietic and lymphocytopoietic tissues become segregated, but they are situated quite separately in different organs, the former being in the ovaries and testes while the latter in The white pulp of spleen and in the subepithelial layer of intestinal mucosa. 3.In the teleost fishes, the kidney becomes the most important organ of graulocytopoiesis, while the chief lymphocytopoietic centers are located in the spleen and in the intestinal mucosa as in the elasmobranchs. No erythropoietic locus is found in any organ at this level. 4.At the still higher level, represented by the urodeles, the three hemopoietic tissues - erythropoietic, granulopoietic and lymphopoietic - become differentiated altogether for the first time, but they are still clearly separated each other. Namely, the erythropoietic tissue occurs in the red splenic pulp