496 D. H. WENRICH 



on account of a misinterpretation of the looped condition of the 

 pachytene threads he decided that synapsis consisted in an 

 end-to-end union. He regarded the longitudinal cleft ot these 

 threads as ha\dng arisen by a sphtting of the individual chromo- 

 meres of the single leptotene threads, instead of arising from a 

 pairing of chromomeres, as I have shown. He failed to detect 

 the formation of the secondary spht, confusing it with the 

 primary, and also failed to notice the zygotene stages with their 

 partially conjugated pairs of threads. 



Gerard ('09), on the other hand, did notice the zygotene stage 

 with the partially paired threads and correctly interpreted them 

 as evidence of parallel conjugation. He regarded one of the con- 

 jugating threads as more prominent "principale" than the other 

 ''secondaire" but I have failed to find evidence for such a dis- 

 tinction. Gerard also noticed that pairing began at the proxi- 

 mal pole and progressed distally, as I have described, and 

 further that orientation was not complete nor entirely persistent 

 in the pachytene stages. 



Meek ('11), in his first paper on the spermatogenesis of Steno- 

 bothrus viridulus, does not commit himself on the subject of 

 synapsis further than to point out the reduction in number of 

 chromosomes in the first spermatocyte and then to say (p. 12): 

 "This reduction must be effected before the breaking up of the 

 spireme, for I have found no evidence of lateral association of 

 filaments after this has occurred," and then (p. 15): ''Probably 



. . . . a numerical reduction takes place as a result of 

 lateral association of chromatin granules or masses on the retic- 

 ulum of tlireads prior to the spermatocyte prophase of mitosis." 

 In a later paper ('12) he concludes that conjugation in pairs 

 actually does take place, though he offers no proof for the state- 

 ment and it is apparent that he has not observed the critical 

 stages. 



McClung ('14) in considering a Stenobothrus-like form along 

 with numerous other species of Acrididae admits the possibility 

 of parasynapsis, but did not make a study of the earlier stages 

 where conclusive evidence is to be found. 



