584 ROBERT T. HANCE 



Anaphase. Clear anaphase figures are exceedingly difficult to 

 find and the chromosomes are likely to be fused as in figures 38 

 and 39, giving a wrong impression of the real conditions. It 

 would appear from these figures that three chromosomes are 

 drawn to either pole, whereas in reality the drawings represent 

 six chromosomes, as shown in figures 35, 36 and 37, the apices 

 of whose V's have fused. In figures 35 and 36 six chromosomes 

 are to be seen being drawn to either pole. Though these appear 

 as rods they are in reality Vs, one arm of which is under the 

 arm figured. In these cases the V-nature of the chromosomes 

 can be determined by focusing. This condition is shown in 

 figure 37a where one of the pairs has been twisted into the plane 

 of the section. Figure 40 shows six chromosomes in anaphase 

 from a polar view. There seems to be a tendency for the ana- 

 phase chromosomes of the somatic cells to turn slightly at right 

 angles to the plane in which they separate, as Whiting has re- 

 ported for the germ cells. In figure 36 the ends of the chromo- 

 somes are all tilted vertically to the plane of the paper. Whether 

 this is due merely to the angle at which the arm of a V might 

 lie or is a real change of axis, I am not certain. 



Artefacts. In all stages of mitosis in poorly fixed material are 

 to be found expressions of the faulty technique. A fairly com- 

 plete gradation of fixation may be found which helps to indicate 

 how other investigators (Seiler and Taylor) may have been led 

 astray in their studies of the chromosomes of Culex. In cells 

 so exceedingly small as these the minute separations would be 

 very quickly obliterated if they were not immediately preserved 

 by the killing agent. The fusion of the chromatin elements" is 

 a very common occurrence unless great care is taken to preserve 

 the tissue properly, as I have shown in a paper to be published 

 shortly on mammalian technique. (Hance '17.) 



DISCUSSION OF RESULTS AND OF THE LITERATURE 



The above account of the somatic mitoses has shown that 

 there are six chromosomes in the body cells, corresponding in 

 size and position to the six chromosomes of the spermatogonia 

 found by Metz ('16) and Whiting (in this journal). In describ- 



