WILLIAMS : BOOPHILUS ANNULATUS. 
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the renal sac begins to appear, growing opaque as the spheres of uric 
acid accumulate in it. As the female becomes more and more dis¬ 
tended with eggs the globules begin to fill back into the tubes and 
their branches, and in the gravid female the whole of the system of 
tubes is full of. this granular deposit. 
The diameter of these filled tubules is not constant. In replete 
forms where each tube can be followed with the naked eye from 
section to section, the same tube may both disappear in one region 
and be greatly distended in another. 
For the usual conditions of the renal tubules see the cross section 
of gravid female (pi. 22, fig. 22). The male tubules never become 
as full of the excretory matter as do those of the female. 
Respiratory Organ. 
The hexapod larva of Boophilus is reported to have no stigmata 
and no tracheae. The adult breathing pores, stigmata, or spiracles 
have been illustrated in section in the general frontal view (pi. 18, 
fig. 4, stig .), and in the discussion of the cuticula (pi. 18, fig. 5). 
From the air space just within the stigma, the air tubes pass inward 
in all directions, dividing into smaller and smaller vessels, which 
twine about all of the internal organs and render gross dissection 
difficult. There are about eight or ten of the large tubes on each 
side. This is well shown by Pagenstecher (’61, pi. 1, fig. 9). 
The main course of the tracheae is forward in the direction of the 
brain, salivary glands, branches of the alimentary canal, and genital 
organs. Each trachea shows a finely cross striate appearance just 
as do the insect tracheae, due to the alternate thinning and thick¬ 
ening of the tracheal wall. This is much the same appearance as 
has already been described for the salivary duct. A trachea in cross 
section is shown in fig. 12 (pi. 20). 
According to Lang, Ixodes has that type of trachea which is 
branched like a tree in the body as in insects and myriapods. The 
air space just within the stigma of Boophilus represents the tree- 
trunk, and the eight or ten large tubes leading from this the 
branches of the tree. 
