416 



SANITARY ENTOMOLOGY 



France. Ixodes hexagonus Leach (reduvius Audouin), and /. ricinus 

 (Linnaeus) Latreille, are suspected to be carriers. The life cycle in the 

 dog was worked out by Nuttall and Graham-Smith (1904-7). The cycle 

 of schizogony is passed in the dog. The free pyriform parasite enters 

 a normal red blood corpuscle and becomes rounded in shape. The parasite 

 throws out pseudopodia and appears as an amoeba. This stage lasts a 

 long time, at the end of which the parasite enters upon a quiescent stage. 

 Finally the organism takes a form called the trefoil stage, in which the 

 main mass of the chromatin, much reduced in size, lies at the base of 

 the two processes. Two nuclei are formed, finally the cytoplasm divides 



LIRE CYCLE OF BABESIA CANIS 



The Cause Of Canine Malignant JaunoicL. 



Fig. 78.— (Pierce). 



and two pyriform parasites are found lying side by side in one corpuscle. 

 The corpuscle now ruptures and liberates the two parasites. 



Christophers has worked out the cycle of sporogony in the tick. When 

 an adult or nymphal tick bites a dog and takes in blood containing the 

 oval parasites, these develop in the gut into round or oval bodies which 

 finally assume the form of a club-shaped bodj' which gradually becomes 

 ookinete. In the adult these ookinetes wander into the ova, while in the 

 nymph they simply pass into the embryonic tissues. In either case they 

 become rounded and form a zygote which breaks up into sporoblasts, 

 and these again into sporozoites which infect the salivary glands of th^ 

 nymph and the adult of the second generation. 



A parent tick having gorged with blood falls to the ground and 



