PRESIDENT S ADDRESS. XCV11. 



ZOOLOGY. 



Experiments and discoveries continue to be made with regard 

 to the minute organisms which are associated with sleeping 

 sickness and other similar diseases, in some cases, such as Malta 

 fever, with great success. The use of atoxyl, an arsenical drug, 

 on which at one time great hopes were built, has had, in 

 experiments, the curious result of developing a race of trypano- 

 somes which are not affected by it. This appears to take place 

 by natural selection, the more weakly ones perishing in enormous 

 multitudes, whilst the few survivors give rise to the atoxyl-resisting 

 race of parasites. It is hoped, however, that in conjunction with 

 other drugs, atoxyl may still be of value. Another minute so- 

 called latent form of this trypanosome has also been discovered, 

 but whether there are sexual forms or not remains uncertain. 

 The report by Professor Herdman on the Ceylon Pearl Fisheries 

 has lately been published, and adds greatly to our knowledge of 

 this subject ; the best pearls are formed round the bodies of a 

 small parasitic worm, though grains of sand and other foreign 

 substances alSo produce them. His investigations in those seas 

 have made known no less than 575 new species of various marine 

 animals. From investigations into the breeding of the common 

 housefly, at times such a pest, it has been found that its full 

 period of development varies from 10 days to five weeks accord- 

 ing to temperature, the places in which it breeds being pits of 

 stable manure (and doubtless ordinary manure-heaps), ashpits, 

 &c., so that, where such places can be cleared weekly, no flies 

 will be produced. Fowls are recommended, as they scratch up 

 and devour large numbers of larvae. The solitary Imperial 

 Entomologist of India appointed to deal with the insect pests 

 affecting that vast empire has lately brought out a report on the 

 subject, containing much valuable information ; but it is to be 

 hoped that the staff may be increased, as the pests in different 

 parts of India would probably be quite different, and far beyond 

 the reach of one individual. A paper published in the Smith- 

 sonian Collections, Vol. 50, deals with the arrangement which 



