498 D. H. WENRICH 



In conclusion it may be said that parasynapsis has been 

 amply demonstrated for Chorthippus through the work of 

 Gerard, Robertson, and myself. The evidence is just as con- 

 clusive for Phrynotettix and Trimerotropis as found by me, 

 while Robertson found clear evidence in Syrbula. Besides these 

 examples from among the Acrididae, parasynapsis was also 

 found among Orthoptera by Otte ('07) for Locusta, by Morse 

 ('09) for blattids, by Vejdovsky ('11-12) for locustids, by 

 Stevens ('12) for Ceuthophilus, and by Robertson ('15) for 

 Tettigidae. 



B. Pre-reduction vs. post-reduction 



The old controversy over pre-reduction and post-reduction 

 which has agitated the minds of cytologists for so long a time 

 seems still far from a settlement. Even without considering the 

 subject of synapsis there has been little tendency to agreement 

 and with the assurance that parasynapsis is the rule in a large 

 number of animals (Wenrich, '16) the uncertainty becomes 

 more acute. There is one thing, however, about which I believe 

 we can be certain, and that is that there is no general rule 

 which is followed by all chromosomes at all times, and a failure 

 to appreciate this fact has had much to do mth the present un- 

 settled state of this subject. I have shown for Phrynotettix ('16) 

 how chromosome-pair C (type Ci) divided by pre-reduction half 

 the time and by post-reduction half the time. In the case of 

 chromosomes A and B the rule was post-reduction, and I be- 

 lieved that post-reduction was the rule for the remainder of the 

 euchromosomes. In that paper (quoted on page 472) I was also 

 bold enough to declare my belief that pre-reduction was the rule 

 with the atelomitic chromosomes of Chorthippus. My greater 

 familiarity mth the atelomitic chromosomes since my study of 

 Chorthippus and Trimerotropis has somewhat shaken my faith 

 in some of the criteria used to determine this point. I am 

 strongly inclined to believe that the mode of division in the first 

 spermatocyte cannot be determined with absolute certainty in 

 the absence of recognizable differences between the two conju- 

 gants of a pair. 



