C. E. MCCLUNG. 



possible to ascertain this positively under any circumstances, but 

 I believe that definite enough information could be secured by a 

 comprehensive study. Considerable importance attaches to this 

 as will be shown later. 



In the Tryxalines the organization of all the cell contents is 

 complete and precise at the time of the first spermatocyte mitosis. 

 Practically the entire cell takes part in forming the bipolar mitotic 

 figure. It is interesting to observe that the greater portion of 



FIG. 14. Portion of a second sperma- 

 tocyte of Mermiria in which the division 

 of the tetrad coming from the decad of the 

 first spermatocyte is shown along with that 

 of the dyads. 



FIG. 15. Anaphase of the sec- 

 ond spermatocyte of Mermiria show- 

 ing the separated dyads of the tetrad 

 and halves of ordinary dyads. 



the cytoplasmic fibers lie outside of the circle of chromosomes 

 that show in a polar view of the metaphase. At this time the 

 chromosomes are scattered along in the spindle, forming no 

 definite plate, and seem to divide independently and unaided. 



This independent action of the chromosomes and the dispro- 

 portion between them and the cytoplasmic figure would indicate 

 apparently that the formation of the spindle is not to produce a 

 mechanism for the separation of the chromosomes, but is rather 

 for the purpose of securing an accurate division of the cell 

 materials. This assumption is further supported by the observa- 



