228 
Argas persicus 
dealing with the anatomy of the coxal glands in A. persicus, our obser¬ 
vations do not agree with her discoveries in this direction. 
Heller* observed two types of alveoli in the salivary gland of 
A. persicus and there is no doubt that he alludes to, and also figures, 
both forms. The alveoli of the second type were first described in detail 
by Bonnet^ who, on account of their resemblance in structure to the 
venom-secreting cells in the poison-glands of certain snakes, concluded 
that they fulfilled a corresponding function, and therefore, termed them 
glandes d venin. Samson has recognised these alveoli, which she terms 
“ Pyramidenzellen,” in I. ricinus^ and also in 0. moubata*. In I. ricinus, 
they are found distributed on the branches of the salivary ducts through¬ 
out the gland, while in 0. moubata, as we have also found to be the case 
in A. persicus, these alveoli—the “Pyramidenzellen” of Samson—are 
collected together in a single mass on the mesial side of the main 
salivary duct at the anterior end of the salivary gland. 
The alveoli of the second type differ from those of the first type— 
the granule-secreting alveoli described above—in the fact that they are 
appreciably smaller in size and instead of being borne on more or less 
long and branching efferent ducts, they are closely applied to the main 
salivary duct, with which they communicate by a short efferent duct 
which, however, shows no difference in structure from the efferent ducts 
of the granule-secreting alveoli. In sections, like the granule-secreting 
alveoli, each appears enclosed by a delicate basement membrane, but 
the secretory elements are markedly different. Both Bonnet and Samson 
described these alveoli as being unicellular. It is true that the indi¬ 
vidual cells are not defined by a cell membrane, but the number and 
arrangement of their nuclei surely indicate their existence. In place 
of the coarse reticulation and granulation of the cytoplasm of the 
granule-secreting cells, these cells show a delicate fibrillar structure, 
the threads of which run from the basement membrane towards the 
lunien of the alveolus. The free margin of the cells is quite indefinite 
and at this point the fibrillar structure appears to merge into a very 
coar.se reticulum, the meshes of which communicate, without the inter¬ 
position of a limiting membrane, with the lumen of the alveolus. The 
nuclei of these alveoli are smaller and fewer in number than in the 
granule-secreting alveoli, and are frequently situated so far from the 
bases of the cells as to appear to be almost free in the lumen. The 
secretion is apparently a clear homogeneous liquid; in any case, large 
- Bonnet A. (1907), pp. 56-58. 
■* Kiinssberg, K. von (1911), p. 264. 
* Heller, C. (1858), p. 308. 
^ Samson, K. (1909 «), p. 203. 
