WILLIAMS: BOOPHILUS ANNULATUS. 
321 
The tendency seen in Id above to pass posteriorly for the second 
time is accentuated in 2b and 2c , the two central diverticula, which 
turn backward at about the region of the genital organs. The pos¬ 
terior end of the alimentary canal as indicated in fig. 7 (pi. 19) is 
not to be seen in fig. 10 (pi. 19). This is because in older ticks little 
or no use is made of the cloacal end of the canal, and so after removal 
of the anal cuticula in dissection the small broken end of the intestine 
was not plain. 
In the young female the body cavity seems completely filled with 
the alimentary canal and its diverticula, but as the animal becomes 
mature the esrgs crowd the digestive system to the wall as shown in 
fig. 22 (pi. 22). 
A cross section of a diverticulum of the alimentary canal of an 
adult female is shown in fig. 11 (pi. 20). The outer layer is con¬ 
nective tissue and within are two sorts of cells : small triangular cells 
filled with granules which stain deeply with haematoxylin, and large 
cells of a more homogeneous structure and with nuclei proportionally 
smaller. 
According to Pagenstecher (’ 61 , pt. 2, p. 31) the pigmented cells, 
which in many cases lie about the alimentary canal, function as liver 
cells. These pigmented cells, however, seem too sporadic in their 
distribution in Boophilus to function actively as digestive cells. In 
many specimens there are none of these irregular pigment masses, 
while the large intestinal cells contain all the pigment. Since sur¬ 
rounding cells are not always to be seen and since the triangular cells 
may be assumed to be glandular in function, as they stain so heavily 
with haematoxylin, I have called them tentatively liver cells (pi. 20, 
fig. 11, cl. hep.). 
The large cells with small nuclei and homogeneous protoplasm, 
which form the main mass of the intestine wall, are certainly the 
usual digestive cells which line any alimentary canal. 
Fig. 12 (pi. 20) is of a section through a diverticulum of the intes¬ 
tine of an adult male. With it are also shown a tracheal tube and a 
renal tubule. In this cross section the hepatic (?) cells are not so 
distinct as in the previous one, perhaps because it is stained with a 
carmine stain. This section illustrates very nicely the stage of 
ecdysis at which I have been successful in cutting sections. The 
cuticula {eta.) has pulled slightly aw T ay from the hypodermal layer 
(Ay.), and that which will be the new cuticular layer {eta'.) after the 
