378 THE PROTOZOA 



unknown in its details, but the transmission appears to be effected by ticks ; 

 so Karyolysns lacertarum by Ixodes ricinus (Schaudinn, A.P.K., ii., p. 339, 

 footnote), H. mauritanica by Hyalomma cegyptium (Laveran and Pettit, 

 718), and the hsemogregarines of snakes (Flu, 707). 



The minute " drepanidia " of frogs and newts appear to stand rather apart 

 from the true haemogregarines ; beyond the fact that they multiply by 

 schizogony in the red blood-corpuscles, but little is known of their develop- 

 ment. According to Hintze, Lankesterdla ranarum has no invertebrate host, 

 but passes from the blood into the wall of the intestine, where it forms re- 

 sistant cysts like a coccidian parasite. The cysts were believed to pass out 

 of the frog with the faeces and infect other frogs by the direct contaminative 

 method. It is, however, very doubtful if the cysts described by Hintze really 

 belong to the cycle of the Lankesterdla ; from other observations it is possible 

 that the drepanidia are not haemogregarines at all, but stages in the life -cycle 

 of a trypanosome (compare Billet, 696). According to Franca (709), " Dacty- 

 losoma " splendens of the frog produces. Leishmania-Mke merozoites, with 

 distinct kinetonuclei (compare also Seitz). Until further researches have 

 been undertaken, the position of the drepanidia must remain uncertain. 



Neresheimer (720) has described the penetration of the red blood- corpuscles 

 of frogs by Lankesterdla sp., a process in which remarkable phenomena are 

 exhibited. When a Lankesterdla, in approaching a blood- corpuscle, is within 

 a distance from the corpuscle about equal to the length of the parasite, the 

 edge of the corpuscle turned towards the parasite shows distinct amoeboid 

 movements. As the parasite comes still nearer, two long processes are 

 thrown out by the corpuscle, forming a deep bay, into which the parasite enters ; 

 as soon as it does so, the two processes approach each other, fuse and engulf 

 the parasite, just as an amoeba ingests its prey. The parasite, after this point 

 is reached, appears to be drawn into the corpuscle without further exertion 

 on its part ; the protoplasm of the corpuscle closes up behind it, and the 

 corpuscle regains its normal smooth contour, with the parasite lying within 

 it. The whole process of penetration takes one or two minutes. Neresheimer 

 compares the activity of the corpuscle to the " cone of reception " formed 

 by an ovum when approached by a spermatozoon. 



From the foregoing account of the life-cycles of naemogregarines, it is seen 

 that the sporogony varies greatly, from the production of eight sporozoites 

 in the oocyst of H. stepanowi and H. nicorice, to the condition of H. cants, 

 H. muris, and H. gerbilli, in which a large number of spores are formed with a 

 variable number of sporozoites. It is impossible, therefore, to accept as 

 adequate the diagnosis given by Leger (644) of the " Hcemogregarinidoe " as 

 producing a single octozoic spore (see p. 353, supra). 



5. The Piroplasms. The parasites of this type are minute 

 organisms, capable of amoeboid movement, but generally of a 

 definite form, which is usually pear-shaped or rod-like. They are 

 contained, sometimes as many as a dozen or more together, within 

 a mammalian red blood-corpuscle. They produce no pigment, but 

 destroy the corpuscle in which they are contained, and set free the 

 haemoglobin, which is then excreted by the kidneys of the host. In 

 consequence of this, the diseases produced by these parasites, 

 termed generally " piroplasmoses " (or " babesioses "), are of a very 

 characteristic type, the most striking symptoms being an enormous 

 destruction of blood-corpuscles and a red coloration of the urine 

 by haemoglobin (haemoglobinuria). From this peculiarity are 

 derived popular names, such as " redwater," etc., applied to 

 diseases caused by piroplasms. 



