784 ILEMOGREGARINA RANARUM 



arranged in groups of three or four at each extremity. Later, the contours of the 

 embryonic parasites appear, the ovoid body divides either regularly or splits up like 

 the staves of a barrel. The embryonic parasites, which may be either free or con- 

 tained in the red cells, are elongated, sometimes slightly bent, swollen at one end 

 and pointed at the other : the nucleus is situated at the swollen end. The free 

 parasites are endowed with movement, thus enabling them to penetrate the red 

 cells. 



Reproduction forms are also found but more rarely, in scrapings from the spleen. 



The reproduction forms of H. stepanowi described by Laveran which represent 

 the endogenous method of reproduction of the parasite are very rarely seen, and 

 this may explain the slight pathogenic properties of the parasite. The exogeneous 

 method of reproduction was for a long time unknown : the disease is not transmitted 

 directly from infected to non-infected animals and infected tortoises do not excrete 

 a parasite capa.ble of living outside the body. According to Siegel H. stepanowi 

 has a second host in a leech (Placobdella catenigera vel Hcementaria cof.tata). In the 

 villi of the hind gut of this leech Siegel found the microgamete stage and oocysts 

 resulting from the fertilization by microgametes of the serpentine parasites found in 

 the blood of the tortoise. These oocysts pass into the blood spaces and thence into 

 the heart of the leech. In the cesophageal glands Siegel found spirilliform bodies 

 which are probably sporozoi'tes capable of infecting other leeches : these structures 

 have also been found in the cesophageal glands of the embryo leeches during vitelline 

 nutrition ; it is probable therefore that the egg itself becomes infected. 



Methods of examination. Laveran recommends the following technique. 



(a) Blood. Blood may be obtained by cutting the end of the tail and 

 should be examined in fresh preparations as well as after fixing and staining 

 (eosin and methylene blue method, ride infra). 



(b) Tissues. Sections give poor results. The following method is 

 recommended. 



1. Prepare a thin film on a cover-glass with the tissue to be examined. 



2. Before drying place the film for 30 minutes in a watch-glass containing 

 a saturated solution of picric acid. Wash in water. 



3. Stain for 6-12 hours in the following mixture, which must be freshly 

 prepared. 



Saturated aqueous solution of methylene blue, 2 c.c. 



Distilled water, - - - - - - 4 ,, 



1 per cent, aqueous solution of eosin, - 8 drops. 



4. Wash in water, dehydrate rapidly in absolute alcohol and mount in 

 balsam. 



Laveran points out that in these investigations care must be taken to avoid mis- 

 taking for parasites the nuclei of nucleated red cells, the unstainable granulations 

 of the red cells of certain fish, chromatin granules which 

 become detached from the nuclei of red cells when the 



^^ blood is badly fixed, and spherical granulations found 



^^J^ Jfe in the red cells of various chelonians which stain deep 



Jfc in the red cells of various ch 

 I violet by Laveran's method. 



2. HoQmogregarina ranarum. 

 Drepanidium ranarum. 



According to Labbe two species of Drepanidium 

 Drepanidium princeps and Drepanidium monilis 

 are found in the frog (Rana esculenta), but Laveran 

 considers that these two forms really represent a 

 single species, H cemogregarina ranarum. The para- 

 site can only be found during the summer and 

 early autumn months, 

 (i) In the blood the adult parasite has the appearance of a vermicule, 12-15/x long, 

 which exhibits active and varied movement. In the resting state the anterior 



