77/A' sriDY or IMIKh'ir.WCH .'><) 



(() tllO other. 'I'lic milk lyotllc shoiiUI iml !»<• Ilinird upside (l(»wii 

 and shaken violently as the haiiaiia ciillure will become loosened 

 and fail with the flies, thus incorporat in^ the Hies within its owr> 

 mass and destroyiiif^ the results of the experiment. In order to 

 move the flies from one container to another, place a hhick cloth 

 al)out the milk bottle and hold the shell vial in the direction of 

 the winilow or .some source of light. The flies hein^; positively 

 phototropic will crawl or fly into the vial where after a few 

 minutes most of them will have assend)led. Lift the l>lack cloth 

 from time to time, making sure that none remains in the milk 

 bottle before removing the vial so as to place the ether plug of 

 cotton into its mouth. A quick transfer is necessary if no Jlies 

 are to be lost. Leave the flies in the etherizing vial for about two 

 minutes or until all the flies have dropped to the bottom and 

 then pour them into the petri dish. The work of separating the 

 sepia-eyed fiies from the wild flies follows, using the dissecting 

 microscope if necessary, after which the count can be made. 

 If flies become active place a small piece of etherized cotton in 

 the petri dish and cover until movements cease. After the count 

 is made the flies should be returned to the milk bottle and // 

 7iot over etherized may be used again. Avoid loosing flies, there- 

 fore, during transfer, and do not leave them in the etherizing 

 bottle too long. 



Before returning flies to the milk bottle compare these Fo 

 flies with the Fx and the Pi generations, which will l)e supplied 

 by the instructors. Write a description of the male parent used 

 in the Pi cross (i.e., a statement of the combination of cliaiaeters 

 which it po.s.ses.'^es). Do the same for the female used in the 

 Pi cross. Also a statement of the characters in which the Fi 

 generation differs from its parents. Then list the number of 

 individuals of each type of Fo progeny. How does this compare 

 with the expected ratio? 



Two plates are provided upon which a summary of this study 

 may be recorded. 



