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bulletin: museum of comparative zoology. 



which was coated with a delicate film of paraffin. This sheet was 



bent so as to form a longitudinal trough, 

 in which the animal was laid surrounded 

 by a piece of paraffined brass netting 

 bent into the form of a tube. Wet filter 

 paper was laid over the netting to keep 

 the worm moist. The occasional change 

 of position on the part of the worms 

 during treatment and the production of 

 secondary radiations from the netting 

 above them both contributed to still 

 greater uniformity of exposure. The 

 gamma rays were so weak as to be negli- 

 gible. For each experiment two indi- 

 viduals of equal size were selected, one 

 for exposure to radium, the other for the 

 control experiment. The one not irradi- 

 ated was placed over an empty cell and 

 in every way, except for exposure to 

 radium, treated like the irradiated ani- 

 mal. The two worms were then fixed 

 and stained at the same time and in the 

 same manner. 



Individuals in three different stages of 

 development were selected for treatment: 



(1) immature worms of approximately 

 one tenth the bulk of the smaller adults; 



(2) adults of rather small size, found to 

 have a well developed clitellum and reproductive organs; (3) large 

 worms with reproductive organs active, taken while copulating. 



That radium has an effect upon AUolobophora is shown in the 

 accompanying table by the death of ten out of twenty-four of the 



Fig- 1- — Diagram of cell con- 

 taining the radium and the 

 cylindrical wire cage to hold the 

 worm used in experiments on 

 AUolobophora. Above, the ap- 

 paratus in cross ssction; below, 

 plan, o, Wire cage; b, radium; 

 c, glass floor of cell; d, sealing- 

 wax rim; c, aluminum roof of 

 cell, so bent as to form a trough 

 to receive the caged worm. 

 Magnified two diameters. 



