THE GONADS OF THE FOWL 89 



a mesenchymal origin for these cells, they arise outside of the 

 ovary, whence they migrate into this organ. While this migra- 

 tion may take place at an early stage in the development of the 

 ovary, their formation within this organ is conspicuous in the 

 embryo of the eighteenth day. Misled by a superficial resemb- 

 lance between the granulocytes and cells which have phagocyted 

 erythrocytes and leucocytes, Firket regards the former as the 

 'histiotopen Wanderzellen' of Danchakoff ('08 a). So far as I 

 am aware, the histiotopic wandering cells do not produce any 

 granules in their cytoplasm ; the inclusions contained in the latter 

 are the result of the digestion of phagocytized elements, which 

 may be granulocytes, while in the granule-laden cells, so abun- 

 dant in the gonad, the granules arise by cytoplasmic differen- 

 tiation. 



Leplat ('12) has also found hematopoietic foci in the vascular 

 membrane of the eye in the embryo, where they arise, according 

 to this author, as a differentiation of mesenchyme cells. Haff 

 ('14) described the origin of granule-laden cells similar to those 

 found in other regions of the body of the embryo in the inter- 

 lobular spaces of the liver, in chicks from the eleventh day of 

 incubation to the end of the embryonic life. The production of 

 granular leucocytes in the liver reaches its maximum from the 

 fourteenth to the fifteenth day, gradually decreasing after this 

 time. 



ORIGIN OF THE EXTRA VASCULAR GRANULOCYTES IN THE 



GONADS 



The facts mentioned in the preceding pages strongly suggest 

 that the granule-laden cells found in the gonads arise as the 

 result of the myeloid transformation of the primitive blood-cells 

 or hemocytoblasts. Since the origin of the latter from mesen- 

 chyme cells has been carefully described by Danchakoff, there is 

 no need of giving a detailed description of the processes involved 

 in their differentiation. The results attained by the writer agree 

 in the main with the descriptions of the observer mentioned 

 above. There are, however, some points which deserve further 

 consideration. The most important of these is the production 



