638 
Wm. S. Marskall 
perpendicular to the surface of the oöcyte. Au examinatiou of a 
cliaiuber after chorion formatiou haa eommenced shows a great cbange 
(Fig. 24), tbe epithelial cells are verv mucb sborteued and are of a 
different sbape. The nucleus bas undergone as marked a cbange as 
tbe cell and, instead of being long, narrow and straight, it bas be- 
corae beut and twisted iuto various sbapes. 
It at first appears Strange tbat epithelial cells from chambers 
older than the one last described (Fig. 21), should be sborter. Our 
study bas sliown us tbat, so far, tbe older tbe chamber the louger 
the cells composing its wall and one might naturally expect to find 
a continuation of this througbout the entire tubule. Shortly after all 
mitosis bas ceased in tbe epithelial cells one notices tbat the nuclei 
which are so prominent in all tbe sections, begin to widen and, if 
compared witb nuclei tbat have reached tbeir maximum length, it 
is noticeable tbat tbese broader nuclei are also shorter (Fig. 22). This 
change seems at first to be equally distributed througbout tbe entire 
nucleus so tbat its outline remains quite regulär. As tbe change goes 
on many nuclei are found wbicb show tbat the basal part bas in- 
creased in width in contrast to its other end wbicb grows thinner 
(Fig. 23). Other nuclei sbow an equal thickness throughout and a 
few bave tbe central part thinner than either end. Chambers still 
older sbow tbat very many of tbe nuclei bave not only sborteued but 
tbat eacli one is, at one or more places, cut in, as if preparing to 
divide amitotically (Figs. 23 and 24). There was no particular place 
where tbe one or more constrictions appeared althougb a large rnajo- 
rity were near tbe middle of tbe nucleus; if but one occurred near 
an end it was most apt to be present in tbe basal region. This con- 
striction, or tbese constrictions, were generally equal from all sides 
although some nuclei showed an indentation on one side without a 
corresponding one at anv other place. 
Düring and following this constriction tbe epithelial cells bave 
become mucb sborter and tbe nuclei must either flatten or they must 
bend. Tbe latter is tbe alternative adopted and we find each nucleus 
bas come to bave an exceedinglv irregulär sbape witb no possibility 
of a regulär outline being found to wbicb very many of tbem would 
conform (Fig. 25). In structure tbe nucleus sbows but little cbange; 
there is an increase in tbe size of tbe nucleoli and a greater regu- 
larity in tbeir sbape. At a stage wben the nucleus bas attained its 
maximum length tbe nucleoli were very irregulär in outline (Fig. 21), 
now they are mucb more rounded (Fig. 25). 
