322 C. E. MCCLUNG. 



a matter of fact one is connected where the accessory joins the 

 tetrad and the other at the opposite end of the tetrad. From the 

 variation in shape of the tetrad portion of the hexad it would ap- 

 pear possible that it has the accessory attached to the side and so 

 divides longitudinally, but this I have not yet determined. Fre- 

 quently it happens that the free extremity of the long accessory 

 chromosome lies near the pole of the spindle, but in metakinesis 

 it is the other end that moves toward the centrosome. In its 



passage from the equatorial plate 

 CiC to the pole this end of the chro- 



mosome is bent upon the other 

 moiety producing a U-shaped 



^M^ 1 \ figure. I have not had opportu- 

 nity*' A) ^^J \ 

 fjl flgfe jfa \ m 'ty to trace the later history of 

 ^P^$i / chromosomes thus associated, 

 ^P J but have little doubt that they 



FIG. 21. Polar view of a similar cell conduct themselves after the 

 with all the chromosomes drawn. manner of similar ones in Hes- 



perotettix. 



It is thus shown that in three of the Orthopteran families, i. c. 

 Acrididae, Locustidas, and Phasmidae (de Sinety) a hexad multi- 

 ple chromosome is found in the first spermatocyte of certain 

 species. Doubtless it exists in many others not yet studied and 

 may reasonably be expected to occur in all the families of the 

 order. In the presence of such elements we may also find an 

 explanation of differences in number and behavior of chromo- 

 somes in related forms and in such as exhibit peculiar chromo- 

 somes not referable to the ordinary types. 



SUMMARY OF OBSERVATIONS. 



1. An Orthopteran family, the Acrididae, is characterized by 

 the possession of a definite and fixed number of chromosomes in 

 its germ cells. 



2. A genus of this family is marked by the arrangement of 

 this series of chromosomes in a characteristic manner, which 

 results in a precise sequence of divisions for these elements. 



3. A species shows the grouping of chromosomes peculiar to 

 the genus, but is distinguished by size differences of chromo- 

 somes, spindles and other cell parts. 



