PERIODIC REORGANIZATION IN PARAMAECIUM 439 



in figure 10 (pi. 1) has seven of these bodies arranged in a semi- 

 circle at the posterior end of the cell. The anterior end contains 

 some irregularly shaped chromatin bodies which seemed to be 

 undergoing involution, while three others more recently ejected 

 are still near the macronucleus. The disintegration of the macro- 

 nucleus progresses until it is entirely devoid of chromatin (figs. 

 35, 36, pi. 4) while the wrinkled and ruptured membrane with 

 but slight staining capacity remains in the cell (fig. 14, pi. 2.) 

 In the later period of the reorganization process the membrane 

 is resorbed and the old macronucleus has finished its function in 

 the paramaecium cell. 



These changes of the macronucleus have their analogy in 

 normal conjugation. There the old macronucleus is destroyed 

 but this is effected by the formation of the so-called "wurst- 

 formige Schlingen," which form a tangled mass of chromatin 

 ribbons. Their origin is figured by Maupas (fig. 10, pi. 12; figs. 

 17-20, pi. 13); and by Hertwig (figs. 6-9, pi. 1; figs. 1-9, pi. 2) 

 and in the present paper (fig. 44, pi. 4) . However, in conjugation 

 it is not until after the animals have separated that the chro- 

 matin ribbons are totally fragmented and more or less spherical 

 bodies are free in the cell. Later an involution of these occurs, 

 the details of which are not described by either Hertwig or Maupas. 

 Likewise, the persistence of the membrane of the macronucleus is 

 not figured by these authors. This ribbon-like formation of the 

 macronucleus we have found to be characteristic of conjugating 

 animals from this race of Paramaecium aurelia (fig. 44, pi. 4). 

 Figure 32 (pi. 3) shows a pair of conjugants with their macro- 

 nuclei in this form. 



In this period then the differences between the macronuclear 

 changes during conjugation and during the process are only mor- 

 phological; on the one hand, the macronucleus forms 'wurst- 

 formige Schlingen;' on the other the macronucleus eliminates its 

 chromatin by extruding it in the form of spherical bodies. The 

 physiological effect is the same. The result is the destruction 

 of the old macronucleus. 



