90 CHARLES R. STOCKARD 



lymphocytes are not seen it is due to poor technique or defective 

 materiah 



Maximow beheves the red blood cells may finally arise from 

 lymphoblasts as erythroblasts, then erythrocytes. This mode 

 of development of the definite erythroblasts continues through- 

 out life and is accomplished in the same manner in all erythro- 

 poetic organs. Wherever such indifferent mesenchyme cells, 

 lymphoblasts, are found this locahty is eo ipso a new place of 

 origin of erythroblasts out of these colorless stem cells. If this 

 be actually true, why then do not red cells, erythroblasts, finally 

 form all through the body of non-circulating fish embryos, since 

 the wandering lymphocytes surely have the power to reach many 

 places other than the normal sites of erythroblasts formation, 

 the intermediate cell mass and yolk islands? 



Maximow claims that both types of blood cells red and white 

 arise at one and the same period from one and the same source, 

 the primitive blood cells in the area vasculosa. The experiments 

 on Teleosts do not bear out such a position since the original 

 or first blood cells from the intermediate cell mass are all erythro- 

 blasts and show a characteristic type at a very early time. The 

 blood origin on the area vasculosa is not so extensive, but here 

 also first form only erythroblasts. 



Supporters of the polyphyletic origin of blood cells have been 

 able to make equally strong observations in favor of their view 

 on similar material to that studied by Maximow, Dantschakoff 

 and other advocates of the monophyletic theory. 



Maximow suggests that since the "primitive blood cell" has 

 no haemoglobin it really stands nearer to the leucocyte than 

 to the erythrocyte, and one might say that the leucocyte arises 

 first in development and the haemoglobin cell later. This is 

 most decidedly not the case in the Teleosts where the primitive 

 mesenchymal blood cell passes directly into the erythroblast 

 without ever showing a stage suggesting either lymphoblast 

 or leucocyte. 



With Weidenreich ('05), Maximow takes the position which 

 he had earlier manitained that all non-granular leucocytes and 

 also the wandering cells of the tissues constitute one great cell 



