HEPATOZOON PERNICIOSUM (N. G., N. SP.)— A H£MO- 
GREGARINE PATHOGENIC EOR WHITE RATS; WITH 
A DESCRIPTION OF THE SEXUAL CYCLE IN THE 
INTERMEDIATE HOST, A MITE (LELAPS ECHIDNINUS 
BERLESE)." 
By William Whitfield Miller, 
Assistant Surgeon ^ U. S. Public Health and Marine-Hos'pital Service, 
Vhaslnngton, D. C. 
INTRODUCTION. 
Although the first of the Hsemocytozoa to be discovered {Lanlces- 
terella ranarum, by Lankester in 1871) was a hsemogregarine, our 
knowledge to-day of this important group is far from complete. 
A great number of hsematozoa have been described in cold-blooded 
animals, in nearly all of which there is a more or less close resem- 
blance to the gregarine type. The most noteworthy peculiarity of 
these parasites is the wormlike form assumed during at least some 
portion of the life cycle. They are, at some period, endoglobular ; 
but they lack the ameboid motion, and pigmentation so character- 
istic of the hsemamcebse. Multiplication occurs by division into two 
or into many individuals. 
Classifying them according to the vertebrate host, the following is 
a brief description of the known species. 
H^MOGREGARINID^ OF AMPHIBIA. 
About ten species of haemogregarines in batrachians are known, 
all of which affect the red blood cells of frogs and toads. Until 
quite recently the belief was unquestioned that sexual as well as 
nonsexual multiplication occurred in the same host. In fact, 
Hintze^ interpreted certain appearances as a conjugation of the 
« Manuscript submitted for publication June 25, 1908. 
& Hintze, R.: Lebensweise und Entwicklung von Lankesterella minima (Chaussat). 
Zoolog. Jabrb., Abt. f. Anat. u. Ontog., Bd. 15, Heft 4, 1904, pp. 693-730. 
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