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1909] GRIGGS—MITOSIS IN SYNCHYTRIUM 341 
is an entirely irresolvable, deeply colored body, whether stained with 
hematoxylin or safranin. Besides the karyosome there may be a 
few deeply staining granules on the nuclear membrane, but there is 
nothing corresponding to the chromatin reticulum characteristic of 
the vegetative nuclei of many cells. The only nuclei in which the 
chromatin approached the condition of a reticulum were located in 
the degenerating cysts occasionally found. 
The spirem 
The early prophases of mitosis consist in the formation of the 
spirem from this compact karyosome. This is brought about in the 
most*direct manner possible. The karyosome first separates into 
a number of irregular chromatin masses (figs. 2, 30); next delicate 
linin bands appear connecting these granules with the nuclear mem- 
brane (fig. 3); and along these bands the chromatin granules are 
distributed over the nuclear cavity, forming the expanded spirem 
(ig. 4 from the same cyst as fig. 2). 
Only a portion of the spirems of Synchytrium, however, are destined 
to pass into mitosis. A large proportion of them undergo nuclear gem- 
mation or some other form of amitosis. In view of theoretical con- 
siderations which will be discussed later, it is of the utmost importance 
to determine whether the spirems of amitosis are of the same nature 
as those of mitosis, or whether they are different in kind and present 
only accidentally an optical similarity. In most cases it is easy to 
distinguish the two sorts by the cysts in which they occur. In those 
cysts which are in the prophases of mitosis, the nuclei are in general 
very nearly the same size and evenly spaced off from each other, 
while in the amitotic cysts there are small nuclei in groups or clusters 
4S well as the large spirems. Many such spirems have a strikingly 
different aspect from the mitotic spirems. They are coarser (jig. 37), 
the chromatin granules are very much larger, and the linin strands are 
short and heavy; whereas the mitotic spirems are characterized by 
linin threads and chromatin granules of various sizes lying side by 
Side. In the amitotic spirems each of the chromatin granules is 
evidently simply the karyosome of a small nucleus, for the formation 
of which the spirem is a preparation. It would thus appear that the 
two classes of spirems are entirely different from each other, but 
