SYNAPSIS AND CHROMOSOME ORGANIZATION 483 



regard these chromomere-vesicles as diagnostic for the apices in 

 this largest pair of V-shaped chromosomes. 



In -the figures from sections (figs. 12 to 14, plate 3) the ap- 

 pendage is attached to only one member of the pair of knobs 

 which mark the synaptic point, and, further, the attachment is 

 always to the knob nearer the middle of the chromatid. In 

 the smears this position is not so evident owing to the lack of 

 definite knobs showing at the synaptic points. However, chro- 

 mosome 9, cell A, does show such knobs and it will be observed 

 that the appendage is attached to the one nearer the middle ot 

 the chromatid. Chromosome 8, cell A also shows such a rela- 

 tionship. The possible evidence that these structures furnish 

 toward an understanding of the planes of first spermatocyte 

 di\dsion will be considered in the discussion. 



g. The accessory chromosome. The accessory chromosome 

 does not require description or discussion in this paper, but 

 attention may be called to the vesicular appendage attached to 

 it. This appendage is similar to those just mentioned which are 

 attached to the atelomitic chromosomes. This structure seems 

 to have been overlooked by all those who have studied this form, 

 except Davis ('08). 



h. Summary. In summarizing the observations on Chor- 

 thippus we may call attention to the follomng: 



1. The number of chromosomes in the reduced series (first 

 spermatocyte) is nine, consisting of one unpaired accessory chro- 

 mosome and eight pairs of autosomes or euchromosomes. Of 

 the latter there are tliree pairs of atelomitic and five pairs of 

 telomitic chromosomes. 



2. The leptotene threads conjugate two-by-two throughout 

 their length during the zygotene, or lepto-zygotene, stages. 

 They remain conjugated through the pachytene stage and until 

 the tetrads are formed. This condition of parasynapsis holds 

 for all the euchromsomes, both telomitic and atelomitic. 



3. The process of parallel conjugation (parasynapsis) appears 

 to be inaugurated at the proximal ends of the leptotene threads 

 as was the case in Phrynotettix, and it appears to begin at the 

 apices of the atelomitic chromosomes. 



