SOMATIC CHROMOSOMES IN VICIA 299 



study. Of this fact Flemming (82) himself was fully aware. After this so- 

 lution brilliant images are obtained by the use of Heidenhain's haematoxy- 

 lin. As the very fine structures retain the color well the préparations are 

 especially valuable for their study. The cytoplasm becomes coagulated into 

 coarse strands and lumps, especially in the central cells. 



Benda's solution is also better for the peripheral cells than for those 

 of the interior, though the différence between the two régions is very much 

 less marked than it is in the case of Flemming's solution. Very good results 

 are often obtained in the inner cells. This is to be connected with the smal- 

 1er amount of acetic acid présent (i %). In well fixed cells the structures 

 stand out with great sharpness, in many cases even greater than after 

 Flemming's solution. This différence seems to be brought about either 

 through a slight contraction in Benda's solution, or more probably through 

 a slight swelling in the case of Flemming's. The finest structures do not 

 retain the stain quite so strongly as atter the latter fluid. Were it possible 

 to use but one fixing reagent for Vicia, this one would be selected. 



The weaker chromo-acetic-osmic solution next given effects the cells in 

 almost exactly the sanie manner as does Flemming's strong solution. The 

 cytoplasm is probably not so greatly altered. Since this fluid contains only 

 I % of acetic acid and still causes a swelling and flowing together of the 

 chromatic structures of the interior cells it is plaiii that it is not the per- 

 centage of the acetic acid alone that is responsible for the bad effects of this 

 solution and of Flemming's, but rather its proportion to the chromic acid 

 (4 : I in this solution, 6.6 : i in Flemming's, in contrast with only i.25 : i 

 in Benda's. The percentage of osmic acid is the same in the last two). 



Bouin's solution also results in a swelling and rounding off of the 

 structures. (Compare the smooth chromosomes from Bouin material in 

 FiG. 32 with those of fig. 31, which are from Benda material.) Conse- 

 quently the finer détails do not corne out as well with this solution as with 

 the above. The spindle is made to appear with considérable clearness, which 

 suggests the value of Bouin préparations for class use. 



Merkel's solution gives very inferior results. The ground substance of 

 the nucleus is not perfectly transparent, and the whole préparation shows 

 a lack of définition. 



Flemming's weaker solution unexpectedly proved to be the most un- 

 satisfactory fixing médium of ail. The stain is removed from the chromatic 

 structures so rapidly that it is impossible to obtain proper differentiation 



