1 66 SECTION B. VERTEBRATA. 



ancestor of the older parent species, rather than to that parent itself. 

 Dr Dixey hoped that in due time Prof. Evvart would communicate 

 further results of his experiments, which raised questions of great 

 interest ; as for instance that of the fertility of hybrids, and that of 

 the alleged phenomenon of telegony. 



Mr P. L. SCLATER said that in his opinion by far the most 

 important of Prof. Ewart's experiments were those which related to 

 telegony, and wished to know whether they had thrown any light 

 upon the question. He then described the differences of the various 

 species of Zebras known to him, and pointed out that hybrids 

 sometimes resembled one of their parents and sometimes the other. 



Prof. EwART replying said that he had tried to find out by his 

 experiments what the less remote ancestors of the Zebra and Horse 

 were like, as in the detailed pattern of the striping the hybrids 

 resembled neither the mother nor the father. 



3. Tsetse Disease in Mammals^ 

 By Prof. Kanthack, Mr Blandford, and Mr Durham. 



This paper, of which the following is an abstract, was read by 

 Mr Durham. 



A bs tract. 



Tsetse disease or N'gana is one of the many scourges of 

 South Africa. Bruce discovered that the cause of the disease is 

 a parasite. It belongs to the flagellated protozoa and to the genus 

 Trypanosoma. According to Bruce's observation the fly merely 

 acts as a carrier ; if it feeds on the blood of an infected animal, and 

 again feeds within two or three days upon a healthy susceptible 

 animal, it communicates the disease. A fact of importance in the 

 dissemination of the disease is Bruce's discovery that the fly is 

 viviparous ; the mother flies have to feed frequently in order to 

 nourish their young. Bruce has further shown that the blood of 

 certain of the wild animals of the "Fly districts" may contain the 

 parasite (e.g. the Koodoo). 



At the instance of the Colonial Office and the Royal Society 

 the living parasite was brought over to this country, where a large 

 number of experiments have been made. 



The inoculation with the parasite not only gives rise to a fatal 

 issue in the horse, ass, ox, goat, dog, and such domesticated animals, 

 but is also fatal to mice, rats, &c., including the hedgehog. The 

 guineapig is able to withstand the infection for several months in 

 some cases. 



The parasite may be present in enormous numbers in the blood 

 of the infected animal, especially in the last few days of life ; in 



^ A more exhaustive report on the subject will be found in the "Proceedings of the 

 Royal Society," Nov. 1898, under title "On Nagana or Tsetse fly disease." 



