Be. AP ee” ey 
1909] GRIGGS—MITOSIS IN SYNCHYTRIUM 347 
reexamined in rapid succession as frequently as desired. The 
favorable cysts so listed number about fifty; most of them contain 
several hundred spindles. 
All of the results obtained were not exactly concordant, but I shall 
give the observations on which the conclusions were based that the 
reader may be enabled to judge of their soundness for himself. In 
all but two of these favorable cysts there were constantly four chromo- 
somes. In these two, however, the number of chromatin bodies 
was certainly more than four (fig. 42). But while the chromosomes 
are all of the same size, some of these bodies were smaller than chromo- 
somes and had the appearance of masses of chromatin from the late 
spirem which had not yet fused together into the compact chromo- 
somes of metaphase. Inasmuch as the spindles were undoubtedly 
newly formed, this is probably the correct interpretation, especially 
as there seemed to be in some cases faint wisps of spirem remaining 
about the equator of the spindle. But whether these supernumerary 
chromatin bodies are to be explained on some such basis or whether 
they are actual irregularities in the number of chromosomes, I am 
of the opinion that they do not seriously weaken the conclusion 
that the chromosome number is four. Although it is unusual for a 
Writer to state difficulties of this sort as frankly as has WILSON (20) 
in his study of Metapodius, seeming discrepancies in the number 
arising from one cause or another are, I believe, frequently met with 
in efforts to count chromosomes. 
In all of the other cysts studied there was no deviation from the 
Constant number four. On all of the spindles the chromosomes were 
Placed at angles of about go°, so that two, three, or four of them were 
Visible, according to the angle of observation (figs. 14-19). In the 
very much larger number of cysts whose spindles were not favorable 
€nough to permit exact counting, there were no indications of a 
different number. It should be noted also that four is an exceedingly 
“asy number to count, for one can see four without counting them 
One by one as is necessary for a larger number. In thus maintaining 
@ Constant number of chromosomes the writer is supported by the 
only other published accounts of the chromosomes of Synchytrium. 
TEVENS in his paper on the primary mitosis (18) states (p. 413) 
that “ they are probably four in number, although we do not assert 
