SYNAPSIS AND CHROMOSOME ORGANIZATION 475 



disarrangements or cuts in the chromosomes. Some distortions 

 natm-ally arise as a result of the smearing process, but the prepa- 

 ration used was more than usually free from such disturbances 

 and in this case the advantage gained through the study of 

 whole cells far outweighs the disadvantages arising from the 

 smearing process. 



In plate 1 all of the chromosomes in each cell are represented. 

 It is believed, therefore, that, although identifications of any 

 chromosome in any cell might sometimes prove doubtful, the 

 chances for error, with all members present, is reduced to a 

 minimum. This method also has its disadvantages, because 

 only occasionally are all of the chromosomes in any particular 

 cell in favorable positions for drawing. 



b. The post-spireme chromosomes. The post-spireme stages 

 have received the most attention and are represented on plate 1. 

 As a glance at the plate will show, there are nine chromosomes 

 in the reduced series. This number has been reported for all 

 the species of the genus which have been studied except the 

 doubtful member reported by McClung ('14) and which he now 

 thinks may be Circotettix in which there were eleven. In plate 

 1, the chi'omosomes of eight cells are represented, those from 

 each cell being arranged in a vertical column according to size, 

 mth the smallest at the bottom. The cells are lettered A, B, 

 C, etc. Each horizontal row therefore presents examples of a 

 particular chromosome, and successive stages in development 

 from the end of the spireme stage to early anaphase can be read 

 from left to right. These horizontal rows correspond in develop- 

 mental stages to figures 62 to 65, plate 6, of the paper on 

 Phrynotettix. 



Of the nine chromosomes in the first spermatocyte one is the 

 unpaired accessory chromosome (no. 3) ; the others are tetrads, 

 consisting of three pairs of atelomitic (nos. 7, 8, and 9) and five 

 pairs of telomitic chromosomes (nOs. 1, 2, 4, 5, and 6). Column 

 A represents the chromosomes of a cell at the stage when the 

 spireme of the growth period has just become distinguishable as 

 indi\ddual segments, each segment being the direct forerunner of 

 a tetrad (except the acccessory, no. 3). Each of the segments is 



