23 



lengthened incubation period four dressings at least should be applied 

 at intervals of four days. Although no disease of horses has as yet 

 been definitely traced to H. asini, there is always the possibility of it 

 proving a carrier. 



NuTTALL (G. H. F.). Observations on the Biology of the Ixodidae. 

 Part iii, Dealing with the Behaviour of the Sexes in Amblyomma 

 hebraeum, Hyalomma aegyptium and Rkipice/plialus bursa when 

 upon the Host. — Parasitology, Cambridge, xi, no. 3-4, October 

 1919, pp. 393-404. 



The observations described show that the male of Amblymnnia. 

 hebraeum remains attached to the host and is sought by the female 

 for pairing. The females only begin to feed to any great extent after 

 this has taken place and they drop off after from 4 to 25 days when 

 fully gorged, whereas the male still remains on the host, only 

 occasionally slightly changing his position, for from 77 to 141 days. 

 In Hyalomma aegyptium and RJiipicephalus bursa the females are 

 sought by the males, which wander over the host, on which they 

 remain indefinitely even after the fertilised and engorged females 

 have dropped off. 



Duke (H. L.). Tsetse Flies and Trypanosomiasis. Some Questions 

 suggested by the later History of the Sleeping Sickness Epidemic 

 in Uganda Protectorate. — Parasitology, Cambridge, xi, no. 3-4, 

 October 1919, pp. 415-429. 



The history of the sleeping sickness epidemic in Uganda and of 

 the suppressive measures adopted against it, as well as the subsequent 

 criticisms of these measures, are reviewed. Both exponents and 

 critics of these methods based their arguments on the belief that 

 complete severance of contact with Glossina was necessary in the 

 ease of human as in that of bovine trypanosomiasis. That this is 

 unnecessary is shown by the comparison drawn between bovine 

 trypanosomiasis as transmitted by Glossina morsitans and sleeping 

 sickness in man as transmitted by G. palpalis. Sleeping sickness 

 may be transmitted by the direct or mechanical method or by 

 cyclical transmission. Observations however show that only in a 

 small percentage of G. palpalis is the trypanosome able to undergo 

 cyclical development. Of the flies ingesting mammalian trypano- 

 somes a smaller proportion of G. palpalis is likely to become infective 

 than of G. morsitans and of such infected flies a smaller proportion is 

 likely to transmit infection in the case of G. palpalis than of G. morsifans 

 to man and domestic ruminants respectively. It is suggested as a 

 plausible hypothesis that the trypanosome persisting in fly and game 

 in Uganda at present is less virulent toward man than that responsible 

 for the decimating epidemic of sleeping sickness. It is not uncommon 

 in laboratory experiments to obtain a strain of trypanosomes of 

 increased virulence and with atypical characters that is able to 

 sur\'ive in animals that previously proved resistant to it^ and there 

 is every reason to believe that such a strain may develop in nature 

 through repeated mechanical transmission and might probably 

 result in an epidemic of trypanosomiasis in a vertebrate host 



