THE GONADS OF THE FOWL 93 



The granulocytoblasts represent a transitory stage in the evo- 

 lution of the extravascular hemoblasts and soon change into granu- 

 locytes or special granular leucocytes. This transformation 

 could be followed step by step in the clusters present in the mes- 

 enchyme. The closely graded series of stages which may be 

 obtained from a single cluster brings forth conclusive evidence 

 on this point (figs. 7 and 15). 



The first manifestation in the production of a granulocyte is 

 the tendency of the nucleus to break into two or more pieces by 

 nuclear constriction followed by the total separation of the por- 

 tions thus detached. The nucleus stretches out in the direction 

 of one of its diameters adopting a more or less marked crescent 

 shape, whose concavity encloses the sphere and the centrioles 

 (fig. 16 and 17). The two halves thus constricted off may per- 

 sist united with each other by means of a connecting strand or 

 separate altogether. This process is accompanied with a deep 

 transformation in the nuclear structure. The karyosome, which 

 is already diminished in size in the granulocytoblasts, shrinks 

 still more in these stages, while the chromatin network develops 

 irregular knots which change into dense masses located in the 

 periphery of the nucleus. The latter shrinks as a whole, becom- 

 ing darker (figs. 2, 5, and 7, g) . Transitional stages between 

 the nucleus with a network and the new condition are even 

 found within the same cell. Sometimes a nuclear portion has 

 already been detached from the main portion of the nucleus, and 

 it shows dense chromatin blocks while the network may still be 

 recognized in the larger nuclear mass. 



A comparison of the nuclei of the granulocytes with those in 

 the intravascular leucocytes reveals a striking similarity. The 

 only difference between the two kinds of cells is the condition of 

 the sphere, which in the leucocytes of the blood-stream persists 

 well developed enclosing the centrioles, while in the granulocytes 

 of the mesenchyme it has ahnost entirely disappeared, leaving 

 remnants in the form of granules in the vicinity of the nucleus. 

 On account of this transformation, the granulocytes have lost 

 their capacity for division and become cells doomed to disappear 

 engulfed by the cytoplasm of phagocytic elements. The presence 



