29 
with a single nucleus. These fibers serve to constrict the ventriculus 
and its diverticula, and in young live mites with transparent scutum 
the waves of contraction, beginning anteriorly and sweeping backward, 
are easily discerned. Adherent to the lining layer in some places, but 
often free in the lumen of the ventriculus, are large spherical cells, 
sometimes called ^fiiver” cells. They possess very small faintly 
staining nuclei, excentrically located, and are phagocytic in nature, 
often containing cell inclusions of various kinds, vacuoles, and yellow 
pigment. According to Berlese'^ they secrete a digestive ferment 
and play an important part in the digestive process. That portion 
of the body not taken up by the digestive and other organs is occupied 
by muscles which move the legs and mandibles and by fat cells. 
The colon, a short, thin-walled tube, terminates in an excretory 
hladder, which communicates with the anus. Opening into the 
lateral aspect of the excretory bladder are paired tubes — the mal- 
phigian vessels — which run forward parallel beneath the ventriculus 
almost to the capitellum, to end blindly. They serve as excretory 
organs, and often contain small dumb-bell shaped cr].^stals of imneral 
salt. 
The salivary glands are paired structures in the body ca^fity, situated 
beneath the anterior extremity of the scutum (pi. vii, fig. 1). Each 
gland is pyramidal shaped and composed of several acini, which are 
formed of large cells of coarse granular structure, with small, indis- 
tinctly defined, deeply staining nuclei. The apex, which is below, 
terminates in a minute duct which empties into the posterior part of 
the pharynx. Each acinus contains a central cavity, which varies in 
size according to the activity of the gland. Small accessory glands 
are sometimes observed. 
Sexual organs. — The ovary is an irregularly shaped, oval body 
situated in the posterior portion of the body. It is composed of a 
reticular framework, in which are many young ova and small cells 
which form the stroma. Projecting from its anterior and lateral 
aspects are ova in various stages of development. Three or four ova 
in advanced stages of development, one of winch is fidly ripened, may 
usually be observed. 
In adult females the uterus, a thin-walled sac lying in front of the 
ovai*}’, usually contains an embryo which may show complete develop- 
ment. The ripe ovum is fertilized in the uterus, winch cominunicates 
by a narrow vagina with the genital apertme. The latter is covered 
by finger-hke sensory organs (pi. iv, fig. 2). Attached to the top of 
the ovary are peculiar tubular structures — the lyrate organs — to 
which are connected a pear-shaped sac (sacculus foemineus) contain- 
“Beiiese, A.; Ricerclie sugli organi e siilla funzione della digestione negli acari. 
Riv. di Pat. Veg., Terenzi; vol. 5 (5-8), 1896, pp. 129-195. 
