176 THE AMPHIBIAN GERMINAL VESICLE 



When the germinal vesicle in weak acid clears^ add a similar amount of weak alkali 

 ( NaOH) and the reactions will he reversed. In NaOH alone the germinal vesicle will hurst. 

 If a very dilute haae is used^ this swelling can he compensated hy acid shrinking. The 

 reactions can he made to go hack and forth under experimental control. 



D. ELECTBICAL CHARGE AND THE EEACTION OF THE GERMINAL VESICLE 



An electrical set-up has heen devised hy means of which a known current may he sent 

 through the germinal vesicle and then reversed. A hrief description of the apparatus is 

 given helow. The equipment consists of a '+5-volt dry cell, a reversing switch, key, 

 platinum electrodes mounted in glass, with voltmeter and milli-ammeter in the circuit as 

 shown in the accompanying diagram on the preceding page. 



Study the electrical set-up hefore attempting to use it, making particular note of 

 the various switches. The milll-simmeter and the voltmeter must he out of circuit at all 

 times and are to he used only hy the instructor to check the apparatus. The student should 

 use only the reversing switch and the tap key . The reversing switch will reverse the direc- 

 tion of the current and the tap key will complete the circuit hetween the points of the 

 platinum electrodes providing there intervenes a conducting (salt) medium. 



Genninal vesicles should he placed on slides in such a manner as to allow a small 

 amount of fluid to flow heyond each side of the Permoplast supported coverslip. The 

 platinum electrode must he immersed in the fluid on each side of the coverslip, and con- 

 sequently on each side of the germinal vesicle. When the ohject is in focus heneath the 

 compound microscope, press the tap key down and hold it as long as you want the current to 

 pass through the solution. To reverse the current simply throw the reversing switch. 

 (See Flndlay: "Practical Chemistry" p. 155 for comparahle set-up.) 



1. Sign of Nuclear Charge ; Use the germinal vesicle of half-sized eggs in which the 

 chromosomes are relatively large. When the vesicle is in position, press the tap key for 

 two-second contact and ohserve the suhstance of the vesicle piling up on the positive (+) 

 side, indicating a negative (-) charge. Watch the migration of the nuclear suhstance and 

 the effect of the release of the current. 



2. Beactions of Chromosomes : If copper (Cu) electrodes are used, which give off hy- 

 drogen ions, sustain the current and note that the chromosomes will pile up at the posi- 

 tive (+) pole while the wall of the germinal vesicle will hurst toward the negative (-) 

 pole, due to the release in that direction of hydroxyl (OH) ions. It would he well to add 

 a deop of phenol red to this solution prior to initiating the current, in order to detect 

 these changes in pH. (It is Important that after each experiment the copper electrodes he 

 thoroiighly cleaned with cotton and acid alcohol, followed hy distilled water, since they 

 will corrode. ) 



5. Comhined Acid and Electric Current : Use the set-up as in #2 ahove hut hefore pass- 

 ing the current through the solution containing the germinal vesicle, add to the N-medium, 

 at a point opposite yourself, a small drop of O.OOIN-HCI. This will hring in the hydrogen 

 ion effect at right angles to the direction of the current. As the I.E. P. passes over the 

 germinal vesicle, apply the current in short shocks. A continuous current will produce an 

 Irreversihle coagulum. Movement Inside the vesicle will he toward the anode will he toward 

 the cathode (-). There will he no movement of the I.E. P. 



