No. 632] CHIASMATYPE AND CROSSING OVER 



219 



jugated threads after crossing over do not untwist, they 

 will give figures like those in Fig. 7 D, and such threads 

 must be pulled apart as Janssens has explained for Ba- 

 tracoseps ; but if after crossing over the twist is rectified 

 as in Fig. 8 A the threads can separate as Janssens ex- 

 plains for the grasshoppers. In both cases the crossing 

 over is represented as the result of twisting threads, and 

 if such loops tend to have a modal length, the mechanism 

 furnishes a beautiful explanation of interference which 

 is one of the crucial tests to which our explanation of 

 crossing over has been put. 



cine-ses de maturation. La celh 

 1919a. A propos de la ehiasmatypie < 



Belg. Biol., 917-920. 

 19196. Une formule simple exprimant c 



la "chiasmatypie" dan 9 les dei 



930-934. 

 CcClung, C. E. 



1914. A Comparative Study of *he Ch; 



1919. The Physical Basis of Heredity. Lippineott Co., Philadelphia. 



1916. Chromosome Studies, I, Taxonomic Relationships shown in the 

 Chromosomes of Tettigidae and Aerididse, etc. Jour. Morph., 

 XXVII, 2. 

 nrich, D. H. 



1916. The SnermahK'.'ii.-is of Pl.ni.mtcttix magnus, etc. Bull. Mug. 



