118 



The Journal of Heredity 



totene threads and hence of quadruple 

 nature of zygotene threads. 



If "change of partners" occurs be- 

 tween the four zygotene elements in 

 various parts of their length, the ex- 

 treme tenuity of the threads may here 

 permit permanent breaks and re- 

 fusions at the points of exchange, giv- 



ing a basis for crossing over which is 

 lacking in later stages, although 

 "change of partners" takes place there 

 also. Relative differences in conden- 

 sation of threads at time of synapsis 

 may therefore explain occurrence of 

 crossing over in one sex and its fail- 

 ure in another. 



Literature Cited 



^Bridges, Calvin B. Non-disjunction as Proof of the Chromosome Theory of Heredity. 

 Genetics, i :2. 1916. 



- Gates, R. Ruggles. Some Points on the Relation of Cytology and Genetics. Joiirl. 

 of Heredity, xiii : No. 2. 1922. 



" Gates, R. Ruggles. A Study of Reduction in Oenothera ruhrinervis. Bot. Gazette, 

 xLvi:i. 1908. 



* Plough, Harold H. The Effect of Temperature on Crossing Over in Drosophila. 

 Jourl. Exp. Zool., .xxiv :2. 1917. 



= Robertson, W. R. B. The Presence of a Longitudinal Split in Chromosomes Prior 

 to Their Union in Parasynapsis. Proc. Amer. Soc. Zool. Abstract 13. Anat. Rec. 

 xvii:5. 1919. 



"Shull, George H. Further Evidence of Crossing Over in Oenothera. Proc. Amer. 

 Soc. Zool. Abstract 116. Anatomical Record, xxiv :6. 1923 



^Taylor, Wm. -Randolph. Organization of Heterotypic Chromosomes. Science, 

 Lxi:i457. 1922. 



''Wenrich, D. H. The Spermatogenesis of Phryuotctti.v }na(inus with Special Refer- 

 ence to Synapsis and the Individuality of the Chromosomes. Bui. Mus. Comp. Zool. 

 Harvard College, lx :3. 1916. 



"Whiting, P. W. The Chromosomes of the Common House Mosquito, Cule.v pipiens L. 

 Jourl. Morph. xxviii :2. 1917. 



Discovery Made Simultaneously By Independent Investigators 



In the two following articles on 

 defective endosperm in maize it seems 

 probable that the authors have inde- 

 pendently discovered the same charac- 

 ter, seeds that germinate on the cob. 

 Further experiments would be neces- 

 sary to prove definitely the similarity 

 of. the two defects. It is interesting if 

 they have found the same character in 

 two distinct varieties of sweet corn, 

 and it is even more remarkable that 

 the mailing of the manuscripts describ- 



ing this discovery was so timed that 

 they both reached us on the same day. 

 Not being gifted with Soloman's 

 wisdom, we have avoided the rather 

 complicated cjuestions of priority in- 

 volved by awarding the baby simul- 

 taneously to both mothers, as it were, 

 and have printed the two articles in the 

 same issue. Since Dr. ]\langlesdorf's 

 manuscript arrived a few hours before 

 Dr. Lindstrom's, we are giving the 

 former priority of place. — Editor. 



