CHROMOSOME STUDIES 207 



1. Syrbula acuticornis Bruner. In the spermatogonia there 

 are (fig. 148) twenty-three chromosomes, consisting of eleven 

 pairs and the sex chromosome. I have numbered the auto- 

 somes in sequence, according to size, from smallest to largest: 

 two I's, two 2's, two 3's, etc. The sex chromosome ranks tenth 

 from the smallest and is therefore marked lOx. The 9's, lO's, 

 and ll's are large. There is a considerable gap in size between 

 the 8's and 9's. The 4's, 5's, 6's, 7's, and 8's form an al- 

 most uniformly graded series. A more considerable gap occurs 

 between the 3's and 4's. The I's, 2's, and 3's form the small 

 series, although a much wider gap occurs between the 2's and 

 3's than between the I's and 2's. 



The chromosomes are all of the rod-shaped type and at meta- 

 kinesis lie at right angles to the long axis of the spindle. In 

 this plane they are arranged in radial fashion around the center 

 of the plate (fig. 148), their pointed proximal ends, to which 

 the spindle fibers attach, turned inward; the large blunt distal 

 ends turned outward. It is important to note this arrangement 

 in making comparison with what is found in Chorthippus. 



I have drawn a series of stages from the prophase to the meta- 

 phase of the first maturation division. Figure 149 is of a nucleus 

 coming out of parasynapsis. There are eleven first-spermatocyte 

 autosomes, each split and more or less twisted spirally, and one 

 sex chromosome (10a;). The latter is also split and may be re- 

 cognized by its condensed condition. The other chromosomes, 

 except nos. 1 and 4, are ahke in having reached about the same 

 stage of unwinding and condensation. No. 1 is farther along 

 than the others, and no. 4 exceeds no. 1, as indicated by its con- 

 densed condition, which approaches that of the sex chromosome. 

 There is a difference between the ends of these conjugated chro- 

 mosomes. One end usually has two dark knobs (x, x), from which 

 the attraction fibers arise, whereas the other lacks any such 

 knobs. These knobs are probably the 'polar granules' described 

 by Finney ('08). 



In figures 150 to 152 a and 153 (later stages) the separation 

 along the split, which was present in the spirally twisted chromo- 

 somes (fig. 149), is much more conspicuous. The spiral twist- 



