REGENERATION IN LUMBRICULUS. 



28.S 



Twelve hours after a worm is cut such a change in the nucleoli 

 near the wound is apparent and by the second day many of them 

 measure at least 2 n in diameter (Fig. 6). Similarly by the 

 second day the nuclei have enlarged until the average of a number 

 measured is 5.1 x 8.8 /*. This increase in the amount of nuclear 

 and nucleolar materials is not confined merely to the wound 

 region but extends even eleven or twelve segments from it. 

 Farther away than this, however, these structures show no 

 change from the size ordinarily present in such a region (Fig. 5). 



Double nucleoli are found in increased numbers within the same 

 limits as are enlarged ones and beyond the twelfth or thirteenth 

 segment from the wound they are no more abundant than in an 

 uninjured individual (Tables I. to VI. inclusive). There is no 

 gradual decrease in number, however, as one gets farther from 

 the wound but a somewhat abrupt drop about the twelfth 

 segment. Mitoses, too, are found only in these same twelve or 

 thirteen segments and, though usually most numerous in the 

 two or three segments nearest the bud, they too do not gradually 

 decrease in number but stop rather abruptly. 



TABLE VII. 



NUMBER OF DOUBLE NUCLEOLI. 



Double nucleoli and mitoses increase rapidly in numbers during 

 the early part of the regeneration period and then gradually 

 decrease again. Double nucleoli have begun to appear on the 

 first day but only one instance of mitosis is found. There is a 

 great increase in the number of each on the second day. By 

 the fourth day, however, the number of double nucleoli has 

 dropped decidedly in the segments more distant from the wound ; 

 this is counterbalanced by an increase in the five nearest segments 



