100 GARY N. CALKINS 



on the other hand divides without mitosis, and shortly after 

 division it breaks up into small spherical or ellipsoidal chromatin 

 masses typical of the resting or vegetative stages. Stages in 

 this re-organization of the resting nucleus are shown in fig. 3. 

 The first fragment formed after division becomes the nuclear 

 granule of the posterior lobe while the micronucleus lies between 

 the first two fragments. These first two parts next divide into 

 two, the four into eight; some divide again, while others do not, 

 the result being from 10 to 14 macronuclear fragments in the vege- 

 tative stages. These nuclear relations are so characteristic that 

 any deviation means an irregularity or abnormality, and they are 

 particularly important in connection with the orientation of frag- 

 ments. 



EXPERIMENTAL 



For cutting Uronychia a small, fine-pointed, carefully sharp- 

 ened scalpel was used. A serrated or ''saw edge" was always 

 avoided. The cell to be operated was first isolated in a small 

 drop of water on a glass slide and then cut under a microscope 

 it was found that, after some practice, a cell could be cut without 

 mangling and in any desired plane. The cut parts were then iso- 

 lated in a few drops of the original medium; these were then cov- 

 ered by a glass coverslip supported on thick glass feet, and the 

 whole put away in a moist chamber. In this way Uronychia after 

 operation may be kept for a week or ten days or longer if necessary, 

 normal forms dividing regularly under similar conditions. As 

 a rule the experimental forms were not kept more than four 

 days, and frequently only until regeneration was complete. The 

 fragments isolated were always carefully studied and sketched 

 to show where and how the knife had passed through. For fix- 

 ing sublimate acetic was used, and for staining the best results 

 were obtained with Delafield's hematoxylin. 



