552 Theophilus s. Painter, 



to end or side by side, there is no direct evidence. From the 

 pachj^tene stage until the telophase of the first division, one may 

 follow the course of the autosomes with ease. 



Pachytene stage. The pachy tene-threads have a very marked 

 loop-shape with the free ends lying near the accessory chromosome. 

 The threads are thick and under very high power they show a 

 somewhat ragged outline. There seem to be nodes and internodes 

 along the length of the threads but no evidence of a split has been 

 seen at this time. Later, the split which gives us the diplotene- 

 threads appears, beginning, usually, in the middle of the threads 

 and running towards the end (Fig. 102). 



Diplotene stage. In this form, the pachytene-threads do 

 not lose their orientation towards the accessory chromosome when 

 the split appears. 



After the diplotene-threads have remained with the shape shown 

 in Fig. 102 for some time, they begin to undergo a contraction 

 during which the autosomes of the first division will take on their 

 characteristic forms. The processes going on at this time are very 

 clearly shown in this spider. 



As the contraction sets in, the diplotene-threads still show the 

 longitudinal split, a general shortening of the threads takes place, 

 and going hand in hand with this we have the two halves of the 

 loop twisting around each other (Fig. 103). This twisting becomes 

 more pronounced as the period goes forward (Fig. 104) until the two 

 halves become very closely coiled about each other. As the con- 

 traction goes on further, we find that the threads are becoming 

 thicker and are beginning to untwist, as shown in Figs. 105, 106 

 and 107. During this whole time one may still see the longitudinal 

 split persisting, as shown by the figures. Later the threads com- 

 pletely lose their twisted shape; but at this time they take the stain 

 very deeply, althongli one may still see signs of the longitudinal 

 split wliich appeared early in the stage (Fig. 108). Part of tlie 

 threads at this time have a ring shape (Fig. 109) while others have 

 a rod foim shown in Fig. 108. 



As the contraction goes still further, there is more thickening 

 of the threads (Fig. 110) and these bodies take the stain very deeply. 

 Usually the split is still clearly seen at this time and we can 

 generally tell what shape the autosome under observation will have. 

 For example, the chromosome shown in Fig. 110, will form a V-shaped 

 body in the early prophase. 



