630 
ffm. S. Marshall 
are all alike iu structure and are also similar to those at tbe corners 
of tlie chambers. If tbey are compared to tbe small elongated nuelei 
of tbe end cbamber tbe structure of tbe two will be seen to be 
identical Daiber (6). 
We find in tbis last mentioned cbamber (Fig. 2 VI) tbat tbe number . 
of the epithelial nuelei bas become mueb greater. Tbis increase takes 
place by mitosis, many sections showing mitotic figures in tbe epi- 
thelial cells; tbese dividing nuelei are never abundant nor do tbey 
occur in groups. Ko amitotic division was observed and tbis incre- 
ase in number of the epithelial cells must come from mitotic division 
of tbe nuelei iu tbe corners and of those which surround tbe oöcyte 
and form tbe wall of tbe cbamber. In tbe follicular epitbelium of 
tbe ovarian tubules of many insects mitosis bas been found and, in 
tbe walking-stick, tbe increase in tbe number of the epithelial cells 
occurs in tbe same way. 
Tbis cbamber we have been describing ;Fig. 2 VI), is tbe first 
one in which a considerable increase in tbe size of tbe oöcyte is 
noticed, all tbe younger ones being of a nearly uniform size. With 
tbis increase in tbe size of tbe ebambers there also goes on an in- 
crease in tbe size and number of the epithelial cells so tbat tbe layer 
surrounding tbe older oöcytes is composed of more and larger cells 
than tbat surrounding the younger ones. There is of course a great 
deal of Variation in tbe number of epithelial cells in chambers of 
practically the same size found in different tubules. Tbe number of 
epithelial cells was counted a number of times in longitudinal section 
of tbe tubule and one count is given as representative of wbat would 
be found in any of them. At first, but two or tbree nuelei are found 
at either side of tbe oöcyte (speaking of a single longitudinal section); 
after tbe regulär layer of cells is found fourteen nuelei can be seen 
on either side. Tbe next oldest cbamber, tbe second one around 
which a complete epithelial layer bas been formed, sbows twenty-one 
nuelei at either side, tbe tbird also twenty-one, tbe fourth twenty- 
seven, tbe fifth forty-three, and the sixtb, seventy-four. Tbe greater 
lengtb of the older chambers is not due so mach to an increase in 
tbe size of tbe cells as to an increase in their number. Later an 
increase in size becomes verv rnarked but growth is tben all in a 
radial direction. 
Auother ebange which takes place as the chambers increase in 
size is in tbe sbape of the epithelial cell nuelei. When tbe epithe- 
lial layer is first formed tbe nuelei are ovoid and lie parallel to tbe 
