102 V. E. EMMEL 



In conclusion, therefore it may be stated that in view of the 

 fact that the cellular elements under consideration in the mesen- 

 chyma are not only deficient in any definite leucocytic granules 

 but that nucleated erythrocytes degenerating in the embryonic 

 tissue spaces may assume cytological characteristics apparently 

 identical with those of the non-granular eosin staining cells with 

 lobulated nuclei in the mesenchyma, it appears difficult to es- 

 cape the conclusion that many if not the majority of the latter 

 just as in the case of the coelomic elements, are degenerating 

 erythroblasts rather than granular leucocytes developing in situ 

 from mesenchymal cells. 



Concerning the distribution of such degenerating erythro- 

 blasts in the embryonic tissues, it is of interest to note that the 

 corpuscles in which the nuclei assume the lobulated condition 

 without becoming noticeably more compact in structure or 

 darker in staining reaction occur typically in the looser tissues 

 with larger intercellular spaces. On the other hand degenerat- 

 ing erythroblasts assuming the more compact forms containing 

 either nuclear rings or dark homogenous nuclear spherules, as 

 previously described, and presenting a great reduction if not 

 entire absence of peripheral cytoplasm occur typically in the 

 denser tissue regions (cf. figs. 39 and 40 with 31-33). Presum- 

 ably the structural characteristics which may be presented by 

 the degenerating erythroblasts are in part determined by the 

 nature of the environment in which such degeneration takes 

 place (cf. however also p. 98). 



In concluding the present subject it may be stated with ref- 

 erence to Maximow's most interesting and stimulating work 

 concerning the participation of the mesenchyma in the formation 

 of blood cells, that while the present results do not in themselves 

 necessarily constitute a conclusive argument against such a 

 possible role of the mesenchyma, they are presented as contrib- 

 uting toward an evaluation of some of the evidence which has 

 been advanced toward the establishment of such a conclusion. 



