446 LORANDE LOSS WOODRUFF AND RH^ ERDMANN 



at the anterior end are figured, can be detected. Figure 39 

 (pi. 4) shows essentially the same stages, the only difference being 

 that the anterior cell has effected one more micronuclear division 

 before the first reconstruction cell division than 16a. 



While the morphological changes which occur after the cell 

 division at the cUmax are clear, those which take place before 

 this division (i.e., from the formation of eight 'reduction' micro- 

 nuclei to the distribution of two to sister cells) must be dis- 

 cussed further. In the instances where two micronuclei remain, 

 it is possible that a micronuclear division has not taken place, * 

 but that merely a shifting of one of the micronuclei into each of 

 the two newly formed sister- cells has occurred. This method 

 of distribution, which- gives an equally satisfactory explanation 

 of the observed data, we call Case lb (text fig. 3). The results 

 of cases la and lb are the same — two cells with one micronucleus 

 and many chromatin bodies at the climax. 



Only twice during these experiments has a paramaecium been 

 observed which had a macronucleus half devoid of chromatin, 

 two well formed micronuclei, two macronuclear anlagen and 

 several chromatin bodies. In these cases the latter were so 

 small and homogeneous that they readily could be mistaken for 

 'reduction' micronuclei. Here it is evident that no division 

 during the climax took place and that the formation of the 

 anlagen has occurred precociously. There are thus two possi- 

 bilities as to the origin of this condition: (a) One so-called reduc- 

 tion micronucleus may remain and divide. The two micro- 

 nuclei thus arising form the anlagen (text fig. 3, Ila). (b) Two 

 so-called reduction micronuclei may remain and divide, thus form- 

 ing immediately the macronuclear anlagen (text fig. 3, lib). 

 The result in either case is the same — one cell with two micro- 

 nuclei and two macronuclear anlagen. 



Data will later be presented (cf. p. 495) which afford strong 

 physiological evidence that a third micronuclear division produc- 

 ing gametic micronuclei (stationary and migratory) must be 

 absent . It is important to note that if no micronuclear division 

 takes place between the last so-called reduction division and the 

 divisions which form the new micronuclei and give rise to the 



