L. E. Robinson and J. Davidson 
227 
duct. In sections of the entire tick, the individual alveoli usually present 
a more or less polygonal outline, due to mutual pressure; in dLssections, 
however, they generally appear rounded and quite loosely aggregated. 
Sections of the gland show each alveolus to be enclosed by a delicate 
basement membrane upon which the bases of the secretory cells rest. 
The latter are large cells, more or less pyramidal in form, whose apices 
are directed towards the centre of the alveolus where they surround a 
small lumen which communicates directly with the efferent duct. At 
the time of maximum activity, the secretory cells are so distended with 
secretion that they encroach upon and almost obliterate the lumen. 
The cytoplasm of these secretory cells is coarsely reticulate, and its 
appearance depends upon the stage of activity of the cell. The nuclei 
are rounded, of moderate size, and are usually situated near the base of 
the cell. In mature cells, they are generally invisible on account of the 
dense mass of deeply-staining ferment granules with which they are 
surrounded. In the same alveolus, secreting cells may be found in all 
stages, from the cell in which the secretory product is just commencing 
to accumulate, to the cell which is literally bursting with its secretion, 
and finally, cells appear, here and there, whose limiting membrane has 
ruptured and the contents of which have poured out into the lumen of 
the alveolus, leaving little else behind, other than the coarse protoplasmic 
reticulum, which stands out, clearly defined, in the now pale-coloured 
exhausted cell. When secretion recommences, such a cell becomes 
progressively darker and rnoi’e opaque, and spherical droplets or granules 
of the secretion appear, in due course, in the meshes of the reticulum. 
As the proce.ss continues, the granules increase in size, and become more 
and more susceptible to the staining action of the basic dyes. By the 
time the final stage is reached, the cell may be so crowded with these 
deeply-staining granules, that all detail of structure is completely 
obscured, the cell appearing in sections as a densely stained wedge- 
shaped sector of the alveolus. From their structure, these secretory 
cells are undoubtedly homologous with the “ Mitndungszellen,” as 
Nordenskiold termed themfi of the salivary gland of I. ricinus. The 
“ Funduszellen” of this author are apparently absent in A. persicus, as von 
Kunssberg^ has found to be the case in OrnitJiodorus moubata. Samson, 
however, has recognised in the coxal glands of 0. moubata, structures 
which she considers to be the homologues of the “ Funduszellen ” of the 
salivary glands of I. ricinus, but, as will be shown subsequently, in 
1 Nordenskiold, E. (1908), p. 647. 
2 Kiinssberg, K. von (1911), p. 265. 
