172 'INFINITE TORMENT OF FLIES' 



after a couple of days fall off. If their mother was 

 infected they nevertheless do not convey the parasite. 

 After lying for a time upon the ground the larval tick 

 casts its skin and becomes a nymph, a stage roughly 

 corresponding with the chrysalis of a butterfly. This 

 nymph, if it has luck, again attaches itself to the dog 

 and has a meal, but it also fails to infect the dog. 

 After a varying time it also drops to the ground, 

 undergoes a metamorphosis, and gives rise to the 

 eight-legged adult tick. Here at last we reach the 

 infective stage ; the adult tick is alone capable of giving 

 the disease to the animal upon which she feeds, and 

 then only when she is descended from a tick which has 

 bitten an infected host. Think what a life-history this 

 parasite has ! Living in the blood-corpuscles of a dog, 

 sucked up by an adult tick, passed through her body 

 until it reaches an egg, laid with that egg, being 

 present while the egg segments and slowly develops 

 into the larva, living quiescent during the larval stage 

 and the nymph stage, surviving the metamorphosis, 

 and only leaping into activity when the adult stage is 

 reached. This most remarkable story probably indi- 

 cates that the Piroplasma undergoes a series of 

 changes comparable to those of the malaria organism 

 when it is inside the mosquito ; what these stages are 

 we do not at present know, but Dr. Nuttall and 

 Mr. Smedley at Cambridge, and many other observers 

 elsewhere, are at work on the problem, and soon we 

 shall have more light. 



With regard to bovine piroplasmosis, Koch, and 

 others have distinguished redwater fever, which is 

 conveyed by Rhipicephalus annulatus, and in Europe 

 probably by Ixodes reduvius from the Rhodesian fever, 

 which is conveyed by Rhipicephalus appendiculatus, and 

 I regret to say by a species dedicated to myself, 

 Rhipicephalus shipleyi. 



The heartwater disease of sheep and goats is 



