252 E. A. ANDREWS 
this is pulled the stylet is raised dorsally into its position of rest. 
Since it lowers the organ into the groove on the thorax it may 
be called the depressor, though it really swings the appendage for- 
ward. 
This depressor muscle is lodged in the protruding ridge of the 
sternum from which the stylets spring, and its fibres are made 
fast to the posterior wall of this ridge. There is also a smaller 
muscle attached to the base of the stylet at its external edge which 
would seem to antagonize the other and to tend to swing the sty- 
let backward, that is, to raise it up from its horizontal position 
of rest into the erect position of use; it may be called the erector 
muscle. ¥ 
The internal anatomy of the stylet as well as the character and 
mode of use of the groove, were made clear from sections. 
The diagram fig. 6 shows the ventral view of a left stylet as if 
transparent, the extent of the glandular area being shaded; the 
glands occur in both external and internal masses, but not in the 
base of the stylet, and they extend from the neck to near the ori- 
gin of the spatula, filling most of the cavity of the region in 
which they occur. 
The sections, (figs. 7 to 13, inclusive), were taken across the 
stylet along the planes indicated by the like numerals in fig. 6. 
The transverse section, (fig. 7) shows in black the exceedingly 
thick shell with the depression on one side that forms part of the 
orifice of the groove, overhung by the solid lip. Through the 
thickness of the shell that forms this part of the orifice are seen 
many fine tubes, passing from the internal glands to discharge on 
the surface. The interior of the stylet is a delicate mass of con- 
nective tissue, chiefly blood sinuses, crossed by few strands of 
tissue, and bounded by the thin epidermis against the shell., 
Seattered all through this are the tubular glands that bend and 
are cut at various angles. These glands ultimately discharge by 
the numerous fine ducts that penetrate the shell. In this section 
the sharp angle above is the ridge (R) seen in figs. 6 and I passing 
along the external mass. The angle to the right is the line be- 
tween the ventral and external faces of the external mass. 
