NOWLIN : CHROMOSOME COMPLEX OF MELANOPLUS. 267 

 MATERIAL AND METHODS. 



The form under consideration, Melanoplus bivittatus Say, 

 belonging to that group of hoppers called Acridiinx, was col- 

 lected in Graham county, western Kansas, in the summer of 

 1904, and forms part of an extensive collection brought to- 

 gether for the purpose of such studies as the present. For both 

 material and direction in this work I am indebted to Dr. C. E. 

 McClung. 



The testes were fixed in Flemming's fluid and stained in 

 Heidenhain's iron-hsematoxylin. Sections were cut six micra 

 in thickness. 



OBSERVATIONS. 



The germ-cells of Melanoplus, as of all other genera of the 

 Acrididx thus far investigated, have twenty-three sperma- 

 togonial chromosomes, twenty-two of which may be paired and 

 the twenty-third without a mate, the typical accessory of 

 McClung. Due to the great crowding in the spermatogonia the 

 exact form of the individual chromosomes is difficult to see, 

 but the general shape is that of a rod. The smallest pair, how- 

 ever, is without exception spherical. The chromosomes are 

 arranged radially around an open center in which occasionally 

 lie from one to two chromosomes (fig. 1), and can with a fair 

 degree of accuracy be paired. The complex is composed of a 

 graduated series of chromosomes whose size relations are well 

 shown in plate XVII. 



In this material the lateral view of the first spermatocyte 

 metaphase is more satisfactory for a comparative study of the 

 chromosomes than the polar view. Since practically all the 

 chromosomes form like tetrads, they cannot with any accuracy 

 be distinguished by form, so here the size test becomes nec- 

 essary. A glance at figures 3a and 3b will show the great 

 variation in size of the chromosomes of a complex. 



For convenience it has been decided to number the chromo- 

 somes according to their size, calHng the smallest No. 1 (fig. 3) . 

 This small chromosome assumes the form of a cross at one 

 stage in its division but completes its changes before reaching 

 the metaphase. It has never been observed in any but spher- 

 ical form here. There is another chromosome which seems to 

 do the same: No. 11, in the metaphase, is always pulled out 

 into the long rod-like form. Running down column 11, plate 

 XVII, one sees this without exception. No. 12 is the largest of 



