440 RIOHAKD EVANS. 



fluid for twenty-four hours, and then washed for an hour in a 

 current of water, and finally brought up through the alcohols 

 into 90 per cent. 



Some of the free-swimming larvae which were held in osmic 

 vapour as above described were afterwards stained in picro- 

 carmine and mounted in glycerine. When transferred into 

 the glycerine the larva tumbled into pieces, and the cells 

 separated owing to the maceration that had gone on in the 

 picro-carmine. In this way free cells were obtained. 



(/) Hermann^s Fluid. — Though I did not use this reagent 

 myselfj I obtained from Mr. Minchin a number of valuable 

 specimens both of free-swimming larvae and of fixed stages. 



After the specimens had been preserved in these various 

 ways, and had been brought into 90 per cent, alcohol, they 

 were then mounted on thin sections of liver. 



The larvse were placed directly on the liver, that is without 

 anything intervening between them, and were covered with a 

 small drop of glycerine albumen, which coagulated in the alcohol. 

 The liver was then cut parallel to the longitudinal axis of the 

 larva, and thus enabled the orientation of the specimen to be 

 made out when sections had to be cut from it. 



The fixed stages, on the other hand, were placed on the 

 liver sections, with the piece of paraffin on which they had 

 settled intervening between them and the liver. In no case 

 were the specimens removed from the paraffin. In this way 

 the whole specimen was mounted, without danger of any part 

 of it being broken away, and the lower surface being always 

 nearest to the liver the manner of fixation could be easily 

 made out in the early stages. After the specimen and the 

 paraffin to which it had fixed itself had been covered with 

 glycerine albumen, the liver section was cut off^ on all sides as 

 near as possible to the specimen so as to reduce its size. 



When the specimens had been placed on liver they were 

 dehydrated by passing them through three successive changes 

 of absolute alcohol, leaving them for about two hours in each. 

 They were afterwards transferred to tubes containing some 

 chloroform at the bottom and absolute alcohol at the top. 



