206 DISPERSAL OF PARASITIC EGGS 



" For the experiments a large cage was constructed. All the sides were made 

 of perforated zinc, except one, which consisted of a large sheet of plate-glass ; this 

 was fixed in two grooves and could be removed. The bottom was of plain zinc. 

 The dimensions of the cage were 3 ft. x i^ ft. x i ft. It was divided into two by a 

 partition of perforated zinc in which was a sliding panel, by which communication 

 could be made between the two compartments. Each compartment was further 

 furnished with a sliding door at the bottom of one side for the admission of flies, and 

 another door at the top, through which they could be removed. For the latter 

 purpose a small square cage with a sliding door was used. This fitted the door in the 

 top of the large cage, and the two sliding panels could be drawn out simultaneously. 

 The object of the cage was to afford the flies as much space, light and air as possible, 

 and it was found that they could be kept alive in it for over a month. The plate-glass 

 side was of use in allowing the experiments to be accurately watched. A few 

 experiments were conducted in a large bell-jar, and in a considerable number of cases 

 glass chimneys, similar to those described by Graham-Smith (1910) were employed. 



"Infective material was offered to the flies in four different ways: i. Fceces 

 containing ova. 2. Complete worms or intact parts of them. 3. Broken or 

 damaged segments of worms. 4. Suspensions of ova in water. 



"The flies which were removed for examination were killed with chloroform 

 vapour. Their bodies and legs were examined for eggs. The legs and wings havini^ 

 been removed, the body was carefully washed in order to get rid of any adhering 

 eggs. The intestine, ventriculus and crop were then dissected out separately. No 

 eggs were ever found in the crop, so that the positive results in the following records 

 refer to the intestine or ventriculus only." 



The carriage of eggs in the iTitestinc of the fly. 



Nicoll's results which are carefully set out in tables, showing 

 the times at which the flies were examined, may be tabulated in 

 the following way. 



TABLE 30. SJiozving the results of feeding experiments 

 zvitJi adult flies. 



In most of these experiments curiously uneven results were 

 obtained. For example in one series of experiments seven flies 

 were fed on ruptured segments of T. serrata and 400 ova were 

 found in the intestines of two flies, two ova in one fly and none 



