294. H. E. JORDAN 
Discussion 
The above-sketched genetic series of events for these giant- 
cells agrees with that previously outlined for these same cells 
both in the yolk-sac of the pig embryo (10) and in the red bone- 
marrow of the rabbit (12). This developmental history is in 
substantial agreement also with that given by Denys for the rab- 
bit’s marrow, and with Heidenhain’s statement that the giant- 
cells of the rabbit’s bone-marrow arise from leucocytes by ‘inter- 
current’ mitoses which never lead to division, but result in 
nuclear refusions following the ‘mother star figure’ (9). 
I have shown in a previous paper that in the yolk-sac of the 
10-mm. pig embryo certain hemoblasts enlarge and become bi-, 
polymorpho-, or multinucleated (12). In the binucleated con- 
dition, which is comparable to a polykaryocyte, these smaller 
giant-cells extensively differentiate endogenous erythrocytes, 
frequently one, occasionally two. These erythrocytes subse- 
quently break through the peripheral shell of the original giant-_ 
cell cytoplasm. Occasionally also in the quadrinucleated condi- 
tion endogenous erythrocyte-formation. occurs. There is some 
slight evidence that quadrinucleated (the usual multinucleated 
condition in the yolk-sac) giant-cells occasionally divide into 
bi- or mononucleated forms before erythrocyte differentiation 
occurs. These giant-cells of the yolk-sac are multiple hemoblasts 
or small blood-islands (figs. 1, 7, 9, 10, 11, 24, 25, 26, and 35 of 
my article on the yolk-sac of the pig embryo (10) and figs 1 to 
24 of my article on giant-cells (12)). A similar occasional en- 
dogenous origin of erythrocytes was described also for pathologic 
(typhoid) human bone-marrow (12). Figure 9, above described, 
also admits of no other obvious explanation than that of endog- 
enous erythrocytogenesis. Since these giant-cells are enlarged 
and modified hemoblasts, it seems plausible that they should 
maintain to some degree their original capacity for erythrocyte 
differentiation under certain conditions. However, this phenom- 
enon of intracellular erythrocytogenesis in giant-cells occurs 
in so slight degree that it does not seem reasonable to ascribe 
to it any essential or even important réle. It seems more nearly 
