370 RESEARCH IN PROTOZOOLOGY 



A light treatment with chloroform is preferable. The chloroformed 

 ones are easily spilled from a test tube on to the slide for dis- 

 section. Living mosquitoes which are not to be dissected may be 

 returned to the cage. Mosquitoes ready for dissection are con- 

 veniently kept in a Petri dish having a moist piece of filter paper 

 on the bottom. 



Dissection of stomachs for oocysts. Use well cleaned slides free 

 from grease. Place a drop of normal salt solution midway on the 

 slide but near the edge away from the observer, and into it place 

 the dead or anesthetised mosquito. Under the lens, remove the 

 abdomen by means of the dissecting needles. The abdomen may be 

 cut off cleanly ; but it is a better plan to dissect it away so that 

 it is opened widely at the anterior end, especially in specimens full 

 of nearly mature eggs. Break the integument of the abdomen near 

 the posterior end, leaving one or two of the terminal segments 

 attached to the gut. Place the point of one dissecting needle on the 

 integument of the abdomen and the point of the other on the 

 terminal segments. Separate the stomach from the wall of the 

 abdomen, using a very slow traction. One may either pull away the 

 abdomen or pull out the stomach from it. 



With a needle placed on the terminal segments, pull the stomach 

 to the middle of the slide. It is easily drawn over a wet surface. 

 With a small piece of filter paper wipe away the drop of salt 

 solution in which the abdomen was dissected together with the 

 eggs and other debris, leaving a thin film of salt solution around 

 the stomach. Brush back the Malpighian tubules with the needles 

 so that they will not overlie the stomach. They remain in position 

 if the liquid is shallow. Place a small coverglass over the stomach 

 with one edge resting on the upper part of the terminal segments. 

 If there is not enough salt solution to surround the gut, add a 

 little at the margin of the cover. 



If the cover rests on the terminal segments the stomach will not 

 be too much flattened. Oocysts will appear on a rounded surface, 

 and the stomach may be easily rolled into a new position by mov- 

 ing the coverglass laterally with a needle. If more flattening of 

 the stomach is desired, the cover may be pressed down. If the 

 terminal segments are not present, it is best to mount the stomach 

 in a larger amount of liquid. One can then flatten the stomach by 

 drawing away part of the liquid by means of a piece of filter 

 paper placed at the margin of the coverglass. 



