Editor's Note : This paper was prepared under the direction of Assistant 

 Professor Kathryn M. Eschenberg, Mount Holyoke College and was accepted 

 by the Faculty in partial fulfillment of the requirements for the degree of 

 Bachelor of Arts with Honor, 1961. Despite certain limitations, described 

 below, the paper (somewhat condensed from the original) has been accepted 

 for publication because (1) it is an unusual and excellent study by an under- 

 graduate, and (2) so little information is available on the subject treated. 

 Biometricians may criticize the paper from the standpoint of small numbers 

 and need for replication. One reviewer says: "One of the most interesting 

 observations related to the apparent increase in resistance following exposure 

 to effectively sublethal levels . Part of the increase, but likely only part, was 

 due to the previous selective killing of weaker individuals. Good experimental 

 procedure would require that this test be repeated, with parallel series of 

 previously unexposed fish. . . .There is need for a replicated study of numbers 

 of young bom to guppies held in DDT. especially because the numbers are so 

 small." It is the Editor's hope that the limitations of the paper may stimulate 

 further work in this important area . 



