Induced Mutations in Habrobracon Eggs

S long ago as 1921 HOLTHUSEN observed an effect of anoxia on X-rayed A cells. Interest in this factor and its relation to radiation damage has recently been revived. BACQ (1951) has reviewed the earlier work and latest developments have been described by HOLLAENDER, BAKER and ANDERSON (1951), HOLLAENDER (1952) and GILES (1952). One group of investigators has been concerned with the question as to whether the reduction in X-rayinduced chromosome injury correlated with reduced oxygen concentration is due to a reduction in primary breaks (breakage hypothesis) or to an increase in restitution of primary breaks (reunion hypothesis). The settlement of this question would aid in understanding the mechanism whereby ionizing radiations produce changes in chromosome structure. Interesting and important facts have been discovered but the question as to the cause of the " oxygen effect " has not been settled. The work on Habrobracon eggs herein reported was undertaken in order to determine if same evidence for one theory or the other could be secured. No proof for either theory has been found but, in the opinion of the author, the facts favor the breakage hypothesis.