THE PROBLEM OF MITOGENETIC RAYS 



923 



of the investigator as to which stage he will accept becomes crucial. 

 To make certain that his counts are correct, Gurwitsch (97) reports 

 that he has taken the following precautions: (a) Each slide was counted 

 several times. (6) Each count was made by some one not acquainted 

 with the results obtained by any other counter. 



The work on the onion root has been repeated with success by several 

 investigators. Reiter and Gabor (229 to 231), Siebert (262), Loos (175), 

 Paul (206), and others. Reiter and Gabor (231) used a somewhat 

 modified technique, and counted all the mitotic stages, thus obtaining 

 a larger body of material for evaluation. They used cross sections 

 instead of the longitudinal sections of Gurwitsch and they found the 

 results clearly positive, although certain fundamental differences were 

 noted. Loos (175) combined the techniques of Gurwitsch with that 

 of Reiter and Gabor and obtained positive results. Paul (206) in an 

 extensive investigation reported positive results also, but she failed 

 to give her experiments the final test of separating the detector from 

 the sender by a quartz shield. 



Table 1. — Effects on Onion-root Activity of Exposure to Onion Sole as a 



Biological Sender 

 The Numbers Represent Counts of Mitoses in Different Sections of Roots 



(Gurwitsch, 97) 



A. Sender: freshly prepared pulp of the medullar plate of onions; detector: 



onion root 



Number of mitoses at 



(a) The "induced" side. 

 (6) The unexposed side. 

 (c) Difference 



45 

 30 

 15 



B. Sender: pulp of medullar plate heated to 60°C., otherwise as in (A) 



(a) The "induced" side. 

 (6) The unexposed side, 

 (c) Difference 



61 



69 



4 



C. Sender: pulp kept at room temperature for 24 hr., preceding exposure, 



otherwise as in (A) 



(a) The "induced" side. 



(b) The unexposed side. 



(c) Difference 



52 



50 



2 



D. Sender: (B) and (C) materials mixed and used at once, otherwise as in (^) 



(a) The "induced" side 



(6) The unexposed side 



(c) Difference 



52 

 40 

 12 



