118 



FERTILIZATION OF THE FROG'S EGG 



B. TIME AND CONCENTRATION RELATIONS 



The preceding experiment is concerned with the dilution factor alone, in which insemina- 

 tion was simultaneous for all concentrations of spermatozoa. In this section the factor of 

 time is also involved, being superimposed upon the various sperm concentrations. In 

 this way the student can determine which of the concentrations will last the longest in 

 terms of giving highest percentage of fertilizations. 



It will be necessary to use #2 covered Stenders for this exercise. These Stenders must 

 be biologically clean and should be properly tested. The covers will tend to reduce the 

 evaporation during the longer time intervals. Secure, wash, and label 28 such Stenders 

 as indicated on the following table. 



TIME/ CONCENTRATION - CLEAVAGE % 



