320 THE DOLABELLINAE. 
lower layers of the cuticle, and gradually decreases, and becomes blended with — 
the strata toward the middle and upper portions. In the outer layers the cuticle 
appears entirely homogeneous, save for the indications of the successive parallel 
layers of deposition from the epithelial cells. 
At intervals among these smaller epithelial cells single gigantic ones are 
to be found, each of which lies at the base of a palatal spine, and apparently 
produces it (Plate 9, fig. 8, b). These cells are usually found at the bottom 
of slight depressions below the general level of the epithelium. This matrix- 
cell often reaches a diameter of 0.10 mm. in width by 0.04 mm. in height, extend- 
ing the full width of the base of the overlying spine (Plate 9, fig. 3). The bulk 
of the cell is finely granular, the upper portion, however, is often more coarsely — 
so, and is sometimes very vaguely limited, being broken up into a mass of 
rounded granules of irregular size, underlying the base of the spine, the whole 
appearance strikingly suggestive of poor fixation, which is very probably the 
case. 
The very large somewhat flattened spheroidal nucleus occupies the basal 
region of the cell, lying close to the basement-membrane. It contains clearly | 
defined chromatin granules, and one or two nucleoli. The basal portion of the 
cell frequently bulges downward below the general level of the epithelium 
and not infrequently extends below the bases of the adjoining cells as in Plate 9, 
fig. 3. In some cases it somewhat resembles a large nerve-cell, but careful 
study fails to reveal any trace of a nerve-fibre proceeding either from or to it. | 
In some sections, near the margin of the base of a spine, such cells appear to be 
subepithelial in position, as is seen in Plate 9, fig. 3, in the large cell adjoining 
spine not shown in the figure. 
All stages of the development of these palatal spines may be found seat- | 
tered irregularly in sections, as each spine passes through its developmental — 
history irrespective of its neighbors. One of the earliest stages is shown in 
Plate 9, fig. 2. The finely granular matrix-cell is smaller than in later stages, 
the matrix-cell of the spine. This is, however, the matrix-cell of an adjoining | 
but is much larger than the adjacent ones. Upon its distal end, which arches — 
above the general level of the surrounding epithelium, is borne a thin cap of a } 
highly refractive substance, the beginning of the young spine. In Plate 9, | 
fig. 4, the matrix-cell has much increased in size, and its chitinous cap has already > 
become so thickened that its substance appears in two layers. The apex of the ; | 
spine is already outlined by the oblique growth of the first strata. In Plate 9, | 
j 
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