1897] Zoology. 69 
alimentary canal the luminal side of each cell is covered by a very 
thick coat of chitin. Through this chitin run a great many minute 
channels which unite to form larger channels and ultimately open into 
the cell. The space into which they open is filled with a homogeneous, 
non-granular substance which stains an intense black in iron hæma- 
toxylin. This substance is limited to the space lying between the 
nucleus on the one side and the chitinous wall on the other and it evi- 
dently fills the channels which penetrate this wall. Its appearance is 
very different from ordinary cytoplasm and I believe it is a form of 
secretion which is being elaborated by the cell to be poured through 
the channels mentioned into the alimentary canal. The proximity of 
the nucleus to this substance, as well as the aggregation of the chroma- 
tin on the side of the nucleus next to it, suggests that the nucleus must 
play an important role in its formation; the nuclear membrane, how- 
ever, is intact on all sides. 
In that portion of the intestinal wall on the ventral side immediately 
posterior to the well developed typhlosole the nuclear membrane is in 
all cases excessively thin on the side of the cell next the lumen, and it 
is usually drawn out into finely pointed processes which become con- 
tinuous with the cyto-reticulum. In several cases which I have ob- 
served the nuclear membrane is altogether wanting on this side of the 
nucleus, and in such cases it can be readily seen that the cyto-reticulum 
is continued into the nucleus, while the chromatin granules, which are 
densest toward the middle of the nucleus, become directly continuous 
with the large microsomes of the cytoplasmic net. This transition of 
chromatin granules into microsomes is most beautifully shown when a 
differential stain such as the Biondi-Heidenhain mixture is used. 
such cases the chromatin granules within the nucleus are green, the 
microsomes are red, and between these the granules shade from one into 
the other through various tints of blue and lilac. It is of course pos- 
sible that in this case the nuclear membrane may be ruptured owing to 
pressure. Against this view, however, may be urged the fact that the 
disappearance of the membrane always occurs at one point, viz. on the 
side next the lumen and furthermore there is no evidence of rupture, 
the structures of the cytoplasm being continued without interruption 
into those of the nucleus. I hold, therefore, that these cells normally 
show a direct continuity between cytoplasmic and nuclear structures, 
though I cannot at present explain the functional significance of this 
fact. 
Finally in the cells of the dorsal wall posterior to the typhlosole the 
nucleus is deeply indented in certain cases on the side next the lumen, 
