30 
ing spermatozoa. The Ivrate organs pass on either side of the 
uterus to terminate upon the inner aspect of the acetabula of the 
coxse of the third pair of legs. 
Since only the female mite is directly concerned in the transmission 
of Hepatozoon perniciosum, the anatomy of the male sexual organs 
will be only briefly considered. The testis is a single oval body situ- 
ated posteriorly between the ventriculus and the excretory bladder. 
The paired rasa deferentia pass downward from each lateral aspect^ 
then forward near the ventral surface, to terminate in the single gen- 
ital opening in the center of the sternal plate. The spermatoza are 
large, round or elongated, granular structures, and are usually found 
in the sacculus foemineus in the female. Here they are stored until 
the ova, becoming ripened one at a time, are fertilized. 
Tracheal system. — The stigmata are placed on the lateral aspect 
of the body, between the third and the fomth pair of legs. A tubidar 
prolongation forward, the peritreme or stigmal canal (pi. iv, fig. 2) 
divides into the main tracheal tubes, which ramify throughout the 
body, some terminating in the legs. The tracheal system is absent in 
the larvae. 
The following articles may be consulted for a more detailed accoimt 
of the structure of the Gamasidse: 
tVinkler, W.; Anatomie der Gamasiden. Arb. a. d. Zoolog. Inst., Wien, vol. 7, 
part 3, 1888, pp. 1-38. 
Berlese, A.: Recherche siigli organi e sulla fiinzione della digestione negli acari. 
Riv. di Pat. Veg., Firenzi, vol. 5 (5-8), 1896, pp. 129-195. 
Michael, A. D. : On the variations in the internal anatomy of the Gamcmdse, e.specially 
in that of the genital organs, and on their mode of coition. Trans. Linnean Soc. of 
Lond., 1892. 
Megnin: Memoire siir Forganization et la distribution zoologiqiie des acariens de la 
famille des Gamasides. Joirrn. d. FAnat. et de la Physiol.. 1876. 
Kramer, P.: F’eber Gamasiden. Arch. f. Xaturg., vol. 1, 1882. 
Michael, A. D. : British T^Togh-phidse. Ray. Soc., 1, 1901, 291 pp. ; II, 1903, 183 pp. 
SEXUAL CYCLE OF HEPATOZOOX PERXICIOSUM IX THE MITE. 
Mites removed from rats (in whose blood parasites were abundant) 
were found, in the majority of cases, to be infected with H. perniciosum. 
Such mites, having fed upon the rat’s blood from time to time, usually 
showed the parasites in seA^eral stages of development. Cross sec- 
tions of mites pictured in pis. ix and x show this condition. Fre- 
quently, when many fully developed parasites were present, young 
forms also were observed in the stomach, indicating a fresh infection 
with each feeding of blood. Mites which were heavily infected with 
fully developed parasites could often be distinguished by the naked 
eye from normal mites. In the former the lateral and caudal portion 
of the body is distended and pearly white, whereas in the latter this 
part is dull brovm in color. 
