WILLIAMS: BOOPHILUS ANNULATUS. 
317 
is marked either distinctly or indistinctly with fine vertical lines, and 
sometimes also shows longitudinal striation. Although the vertical 
lines cannot be seen to pass through the opaque outer layer, in ticks 
which have not lately shed or at sharp bends of the cuticula in almost 
all specimens, the outer layer opens in crevasses or cracks which 
match the lines seen on the surface in fig. 3 (pi. 18). 
The cuticula, then, is traversed by numerous openings for glands 
and for hairs, by four porose areas in the case of the female, by two 
spiracles or stigmata, and by the oral, genital, and anal openings. 
A section through the stigmatic plate (pi. 18, fig. 5), taken on 
one side of the stigmal opening, shows the arching cover over the 
air space beneath supported by numerous pillars of chitin. These 
pillars cut off small chambers above the hypodermis which may pos¬ 
sibly connect with the central air space and increase its capacity. 
At this stage in the description it will be useful to introduce a 
frontal section of a small female (pi. 18, fig. 4), to show the general 
relationship of the internal organs. The capitulum was bent down¬ 
ward out of the plane of section. The palpi, brain, one of the sali¬ 
vary ducts and many of the individual salivary glands, the region of 
the ovary and genital passages, the stigmata, and the accumulation 
of excreta in the renal sac are shown as they lie in the animal. 
Musculature. 
The musculature of the tick is definitely related to the shapes of 
the internal organs, especially the alimentary canal and the excre¬ 
tory system. 
The most evident systems of muscles are dorso-ventral. These, 
by their insertion on the ventral side of the body make in the female 
the two diverging lines on the ventral cuticula which can be fol¬ 
lowed from the corners of the genital opening backward to the pos- 
tero-lateral portions of the abdomen. A shorter row of similar 
dorso-ventral muscle fibers extends in the mid line from the anal 
opening to the posterior edge of the abdomen. The insertion of 
these systems of fibers on the dorsal side of the animal is not so 
regular and produces various patterns on the slightly collapsed 
abdomens. The postanal row is made up of straight dorso-ventral 
fibers, but those in the lateral rows may slant toward the front before 
they are inserted on the dorsal wall. 
