STUDIES ON CHROMOSOMES. 24! 



where slight shifts of focus are possible, are just as clear cut 

 cases as photo 8, although because of foreshortening of the object 

 as seen in one plane, not one of them gives as convincing a 

 photograph. 



Figs. 152-158 and photos 30-32 are polar views showing the 

 X-like body lying at the edge of the equatorial plate. If such a 

 cell were being viewed from the side instead of the pole it is 

 obvious that the special element would in all likelihood be in- 

 detectable and such a view would probably, by one who desired 

 to make a case against the existence of such a body, be recorded 

 as evidence against it. Such side views must of course occur, 

 but in even many of these a careful scrutiny of the mitotic figure 

 shows that it is asymmetrical, extending out further on one side 

 from the spindle than on the other. In such instances it is as 

 legitimate to infer that one has in the chromatic band before 

 him a special element related to the other chromosomes as in 

 Fig. 157, as it is to consider it in any other way. Or in any 

 event it can not be legitimately recorded as evidence against the 

 existence of such a body. It is obvious further that if such an 

 element as shown in Fig. 157 lay directly back of or in front of 

 the other chromosomes as viewed by the observer, instead of at 

 the side, the equatorial plate would then appear symmetrical 

 and such a stage, though having the element in question, would 

 be likely to be recorded as without it. 



Photo 33 shows a telophase of a dividing primary spermatocyte 

 in which the undivided X-element lies close to one set of the 

 divided chromosomes after the latter have migrated to their 

 respective poles. The opposite pole has no such body. Photos 

 34 and 35 show somewhat similar conditions, only in these 

 cases matters are complicated by the beginning of the secondary 

 fusion of chromosomes w y hich is so characteristic a procedure 

 preliminary to the next division. In such cases, of which a 

 number have been observed, the X-like element is apparently 

 tied to the rest of the adjacent chromatin mass by two heavy 

 linin fibers (Figs. 151, 164, photo 34). It is possible that this 

 is determined by the fact that the curved chromosome is in 

 reality probably double in nature. Figs. 150, 151 and 164 are 

 camera-lucida drawings of such conditions showing details that 

 could not be revealed by photography. 



