180 



ANDROGENESIS 



REMOVAL OF THE FEMALE NUCLEAR ELEMENTS 



An ovulating female frog is secured and concentrated frog sperm suspensions are pre- 

 pared as thin films in 4 Syracuse dishes. When the optical equipment is adjusted, strip 

 a few of the eggs from the female into one of the Syracuse dishes. At 10 minute intervals 

 strip additional eggs into other Syracuse dishes, marking the exact time of insemination 

 on each dish. Within 3 to 5 minutes after insemination, flood each dish with Spring Water 

 (or Standard Solution) so that the eggs are completely covered. The other dishes are to 

 be similarly flooded at comparable intervals thereafter. The water on the eggs may be 

 changed to clear it of excess spermatozoa. 



The nucleus is to be pulled out by means of a glass needle. This needle should be made 

 of soft glass but must have a sharp and rigid point. A large number of needles should 

 be made available with an appropriate needle holder. 



When the egg is inseminated the first polar body is already located between the egg and 

 the vitelline membrane. This small gray bead representing an extruded nucleus may 

 sometimes be located on the animal pole surface, near its center. One must focus very 

 sharply onto this animal pole surface, and use light coming onto the egg from an angle, 

 in order to see the very small polar body and its shadow. 



CAPIL.1_ARY PIPETTE SEE KAYUOR '39 



ANIMAL POLE 



METAPHASE FIGURE 



VITELUANE MEMBRANE 



SEE PORTER '39 



