Katharine Foot and E. C. Strobell 301 
tocyte in which its identity is assured, through the prophases, metaphase, 
anaphase, and telophase of both divisions. We believe we have shown 
good reason to doubt the interpretation of Wilson and Montgomery that 
normally this chromosome does not divide in the second spindle, but 
passes over undivided to one of the daughter cells. The evidence that 
our preparations furnish for this position is given in full in the above 
detailed description of the eccentric chromosome and we shall close this 
description with a brief summary of the important points: 
First, in the resting first spermatocyte we see no evidence of a per- 
we find all the chromosomes with- 
sisting spermatogonial chromosome 
out exception following the typical course of development which has 
been demonstrated for so many forms, 7 e., through this period the 
identity of the individual chromosomes is completely obseured—the chro- 
matin being diffused throughout the nucleus, later forming a chromatin 
reticulum which passes through definite changes culminating in the 
reappearance of individual chromosomes. 
Second, we find only one body in the rest stage that in any way re- 
sembles the dense deeply-staining nucleolar-like structure interpreted by 
Wilson and Montgomery as a persisting spermatogonial chromosome and 
this body we interpret as a plasmosome and not a chromosome. 
Third, in the prophases of the first spermatocyte we have been able 
to demonstrate a special chromosome (which we have called the eccentric 
chromosome) persistently maintaining a form which assures its identi- 
fication throughout these stages, and this chromosome does not in the 
least resemble the body figured by Wilson as the heterotropic (eccentric) 
chromosome of these stages. 
Fourth, although the eccentric chromosome of the prophases usually 
appears as two thin parallel rods we have been able to demonstrate that 
it may also appear as a tetrad, showing the secondary furrow common 
for the other large chromosomes—the furrow interpreted in all other 
forms as foeshadowing the plane of the second division.’ 
Fifth, we have demonstrated the secondary furrow in the eccentric 
chromosome not only in the prophase of the first spindle but at the 
anaphase and telophase of this spindle and at the prophase and meta- 
phase of the second spindle, this secondary furrow or constriction 
* Wilson has observed the exceptional appearance of the tetrad form of this 
chromosome, and Paulmier mentions its tetrad form without any note of its 
being exceptional. 
