388 
Avgas persicus 
the act of defaeeation, the extrusion of ova in the female and sperma- 
tophores in the male, and of the glandular secretions—all these 
functions call in the aid of the body-muscles. 
For the most part, the dorso-ventral body-muscles occupy the 
marginal regions of the body, where their presence is indicated externally 
by the marginal discs present on both the upper and lower surfaces of 
the body. The general direction of the rows radiates from the central 
point of the body as is clearly shown in the figures (see Text-figs. 2 
and 3). 
The marginal dorso-ventral muscles ( m.mg .) extend round the whole 
circumference of the body, their arrangement being more or less irregular 
in the anterior and lateral regions, but forming fairly regular rows in 
the posterior region. From their relations, it is evident that they 
correspond to the muscles which form the marginal grooves and the 
festoons of the Ixodid ticks. In their course through the body- 
cavity they pass between the terminal saceulations of the alimentary 
coeca. 
The postero-median dorso-ventral muscles (rn. p. m.) form a longi¬ 
tudinal series, which extends from the anus to the mid-point of the 
posterior margin of the body. They form a median partition in the 
posterior half of the body, which separates the postero-lateral alimentary 
coeca and the diverticula of the rectal sac. The postero-accessory 
muscles ( m.p. a.) commence at a point on either side of, and posterior to, 
the anus, from which they run backwards and terminate some little 
distance from the body margin. At the anterior end of the series, the 
muscle columns are generally aggregated into a cluster, a condition 
which is further developed in the genus Ornithodorus. These muscles 
correspond to the similarly situated muscles of the Ixodidae which form 
the postero-median and the postero-accessory grooves. 
The camerostomal muscles (rn. cam.) take their origin in the dorsal 
integument, anterior to, and on either side of, the part which overlies the 
capitulum ; their function, in all probability, is to facilitate the exposure 
of the capitulum during the operation of feeding, by retracting the 
camerostomal folds into which their lower extremities are inserted. 
The spiracular muscles (omitted in Plate XXY) each consist of a 
single thin slip, the upper end of which is attached to the dorsal integu¬ 
ment, the lower extremity being attached by a short tendinous insertion 
into the wall of the atrial chamber. 
The dorso-genital muscles (m.gen'.) originate on the dorsal integument 
and are inserted at their lower extremities into the ventral body wall, 
