84 Edmund B. Wilson 



chromosome. Concerning the first point I will here only indicate 

 one principal conclusion. It is quite clear that in Pyrrochoris 

 (and I think the same holds true in other Hemiptera) synapsis, 

 or the conjugation of chromosomes two by two, does not occur in 

 the closing anaphases of the last spermatogonia! division as was 

 described by Montgomery ('00) in Peripatus and Euschistus 

 ("Pentatoma"), by Sutton ('02) in Brachystola, by Stevens ('03) 

 in Sagitta, and by Dublin ('05) in Pedicellina. Although the 

 number of chromosomes in the postphases immediately following 

 this division (Photos 32 and 33) cannot be exactly made out, it 

 is perfectly evident that it is not the reduced number but approxi- 

 mates to the somatic number (twenty-three). The chromosomes, 

 therefore, have not paired two by two in the spermatogonia! ana- 

 phases. It is equally certain that this stage does not pass directly 

 into the synizesis but is separated from it by a long " resting period" 

 (Photos 34 to 38) — as is demonstated by the topographical 

 relations as well as by the progressive stages of the idiochromo- 

 some — in which the ordinary chromosomes lose their sharp 

 boundaries and their affinity for nuclear stains. In this respect 

 Pyrrochoris shows a close similarity to Tomopteris, as described 

 by the Schreiners ('06), whose original preparations, by the 

 kindness of Dr. Schreiner, I have had opportunity to examine. 

 This comparison has convinced me that synapsis occurs at the 

 same period in both — ^whether by parasynapsis (side to side union) 

 or telosynapsis (end to end union °) or in some other way I am 

 not prepared to say. There can be no manner of doubt that 

 the first division of the bivalents is a transverse one, as described 

 by Paulmier and Montgomery; but it has been rendered evident 

 enough by recent studies on reduction that this in itself gives no 

 trustworthy evidence regarding the mode of synapsis. The 

 direct investigation of the process in the Hemiptera presents 

 great difficulties. 



The foregoing general conclusion regarding the time of synapsis 

 is of importance for the more specific one in regard to the idio- 

 chromosome. During the entire earlier presynaptic period the 



' I have for some years made use of these terms in my lectures on cytology. 



