L. E. Robinson and J. Davidson 
409 
contraction of the uterine muscles, and gradually the ovum is manipu¬ 
lated by the action of the complex arrangement of muscles surrounding 
the cervical portion of the vagina, first into this portion of the vagina 
and then to the base of the ovipositor, the final extrusion being brought 
about by the contraction of the dorso-ventral body-muscles, particularly 
the dorso-genital muscles. A copious secretion of fluid by the accessory 
glands serves to lubricate the terminal portion of the vaginal canal, and 
thus to facilitate the passage of the eggs. 
The eggs of Argas persicus are almost spherical in form, and have 
a diameter of 0'6-0\8 mm. The shell is dark yellowish-brown in colour 
a'nd its external surface is ornamented by a very delicate reticulation 
which is generally concealed by the adherent moist secretion of Gene’s 
organ. 
Gene’s Organ. 
Plate XXVI, figs. 8-10, Plate XXVIII; see also 
Part II, Plate XIV, Gen. org. 
Gene’s organ, so named by Nuttall 1 in honour of its discoverer 2 , 
is solely concerned in the act of oviposition and is, therefore, peculiar 
to the female tick. It is, we believe, universally present in all the 
Ixodoidea, and has been the subject of more or less detailed considera¬ 
tion in most of the works dealing with tick anatomy in recent times. 
It has been described under various names —cephalic gland, subscutal 
gland, ovipositing gland, and others; and has, moreover, been the 
subject of some very strange and erroneous conceptions. 
The organ makes its first appearance during the final nymphal 
moult, but only attains its maximum development by the time that 
the sexual organs have acquired their full activity. It consists of a 
pair of eversible membranous sacs, derived from the chitinous cuticle 
of the body, which in the non-active state are contained within a pair 
of similar sacs of hypodermal origin, and into which the efferent ducts 
of a pair of large glands opens. Gene’s organ is situated entirely in 
the anterior part of the body, its median portion lying immediately 
above the anterior margin of the capitular foramen, while the glandular 
portion extends laterally and posteriorly for some distance within the 
body cavity. 
It has already been seen (Paid I, p. 34; Plate III, fig. 7) that 
the external opening of Genb’s organ is a broad crescentic slit with 
1 Nuttall, G. H. F. (vn. 1908), p. 16 repr. 2 Gene, G. (1841). 
