author's abstract of this paper issued 
by the bibliographic service, november 15 
FURTHER STUDIES ON THE EFFECT OF 
TEMPERATURE ON CROSSING OVER 
HAROLD H. PLOUGH 
Department of Biology, Amherst College 
THREE FIGURES 
CONTENTS 
Introductory 187 
Experimental 188 
Interpretation of the curves of crossing over 189 
Reaction to temperature and high coincidence 194 
Discussion 198 
Age and temperature effects compared 199 
Summary 201 
INTRODUCTORY 
In an earlier study of the effect of temperature on crossing 
over in Drosophila melanogaster I showed that temperature 
both above and below the optimum (22°C.) caused a significant 
increase in the amount of crossing over between certain genes 
located in the second chromosome (Plough, '17). Prehminary 
work on the first and 'third chromosomes indicated, however, 
that crossing over in these groups was not visibly affected by 
temperature. No reason for this unexpected result could be 
assigned, and it seemed worth while to test the first and third 
chromosomes by the same accurate methods which had been 
used with chromosome II. Such data would also give an accurate 
basis for checking the fact reported by Bridges ('15) that in 
chromosome I, unlike the second chromosome, there is no signifi- 
cant variation in crossing over due to the age of the female 
parent. 
The large amount of breeding work with Drosophila has 
resulted^ — especially through the work of Bridges — in making 
available a large number of easily workable mutant characters 
187 
