112 HARRIET RANDOLPH. 



shown, together with the heterochromosome pair and the plas- 

 mosome. All are from the same cyst. Figs. lo, ii and 12 are 

 from late prophases of the first spermatocyte division. The 

 chromosomes arrange themselves into two groups at opposite 

 poles. This is shown in Fig. 10, where the black bodies repre- 

 sent one group and those in light outline are 180° away, while 

 the one in heavy outline is approximately at the equator. Figs. 

 II and 12 show a centrosome close to each group which had 

 apparently moved with its centrosome to that position. That 

 the final position of any chromosome at one or the other of the 

 poles is due to the centrosome in whose sphere of influence it 

 happens to lie is suggested by the fact that occasionally seven 

 chromosomes are at one pole and only five at the other. 



In the equatorial plate of the first spermatocyte division there 

 are normally twelve chromosomes (Fig. 13). In two or three 

 earwigs a few cells of a cyst show eleven, thirteen, sixteen or 

 nineteen chromosomes in the equatorial plate of this division ; 

 but there are also present in these cysts tripolar or multipolar 

 spindles which probably explain the irregularity. There are 

 also occasionally giant nuclei with double the normal num- 

 ber of chromosomes. In one case of an abnormal spindle it 

 is known that the material came from an earwig that had very 

 recently moulted, and it is possible that there is a connection be- 

 tween the two facts (Riddle, '08). In one instance a tripolar 

 spindle was observed also in a spermatogonial division. 



In the anaphase of the first spermatocyte division the hetero- 

 chromosome pair are late in dividing and lag behind the others 

 (Figs. 15, 16, 17). They are about equal in size. They finally 

 separate (Figs. 18, 19, 20), one going to each pole of the spindle, 

 and pass into the prophase of the second spermatocyte division 

 (Fig. 21). Here again the chromosomes show a tendency to ar- 

 range themselves at the poles. Fig. 22 shows the metaphase 

 and Fig. 23 the equatorial plate of the second spermatocyte divi- 

 sion with twelve chromosomes. Figs. 24 and 25 are from 

 stages in the anaphase. The earliest stages of the spermatids 

 are shown in Figs. 26, 27, 28 and 29, where the behavior of the 

 archoplasm and the change in position of the centrosome 

 can be seen. Fig. 32 shows the condensed chromatin body in 



