Exercise XXII 



INTRODUCTION TO GENETICS OF MAN AND FRUIT FLY 119 



tion. Two of these are: (1) The pieces of the 

 animal retain the polarity they had in the whole 

 animal; a new head grows from the end origi- 

 nally nearest the head, and a new tail from the 

 end originally nearest the tail. (2) Pieces cut 

 from near the head regenerate better than those 

 from near the tail. Your own experiments can 

 demonstrate both points. It has been suggested 

 that differences in the rate of metabolism, graded 

 downward from the anterior end, may explain 

 the polar nature of regeneration. The regenerat- 



ing parts at first lack the pigmentation of the 

 original tissue and are thus easily recognized. 



Planarian monsters possessing two heads or 

 two tails can be made by slicing the animal 

 parallel to the long axis of the body, the cut 

 extending about a third of the body length, 

 either through the head or through the tail. 

 Since there is a great tendency for the divided 

 parts to rejoin and heal together, the slit should 

 be reopened every day if necessary. 



EQUIPMENT' 



Per laboratory 



prepared slides demonstrating meiosis and mitosis 

 stained preparations of salivary glands of Drosophila 

 larvae 



ether in dropping bottles 



PTC paper 



white cards 



dissecting microscope for each student 



etherizers t and re-etherizers 



"morgues" (jars containing kerosene oil) 



razor blades 



camel's hair brushes 



Dugesia dorotocephala (2 or 3 per student) 



petri dishes (2 or 3 per student) 



solution of bicarbonate, versene, and tap water 



(BVT), prepared as follows: 



(1) NaHCOs (2 gm/100 ml); sodium (di)ethylene- 



diamine tetracetate (sodium versenate) 1 gm/100 



ml 

 (2)CaCl2(1.5gm/100ml) 



To prepare 1 liter of BVT, put 5.0 ml of solution 

 (1) and 5.0 ml of solution (2) into some hot tap 

 water, and then make up to 1 liter with hot tap 

 water. (Using hot water gets rid of the chlorine 

 faster.) The solution can be used after standing 

 overnight. 



*Detailed information about designing experiments with Drosophila and obtaining stocks can be found in 

 the Drosophila Guide, by M. Demerec and B. P. Kaufmann, which can be obtained for 25^ from the Car- 

 negie Institution, 1530 P St. N. W., Washington 5, D. C. 



fEtherizers can be made from small, wide-mouthed bottles to the corks of which have been tacked bits of 

 cotton. Polyethylene anesthetizers can be bought from Burdick Drosophila Supply Co., 250 Lincoln Street, 

 West Lafayette, Ind. 



