ROLE OF NUCLEUS IN CELL FUNCTIONS. 383 



upon any phase of cell activity is by removing it, and observing 

 any variations from the normal in the behavior of the cell. 



A. Gruber (1886) was perhaps the first to cut an amoeba into 

 two pieces for the purpose of observing the effect of the removal 

 of the nucleus upon locomotion. He says (free translation), 

 "The part with the nucleus continues to project and withdraw 

 its pseudopods, as before but the part without a nucleus with- 

 draws its pseudopods although there is a weak streaming at first. 

 Two days after the bisection the (enucleated) amoeba died." He 

 concluded that the experiment showed that in amoebae the capac- 

 ity for movement is affected, which he had found was not true 

 in the case of the Infusoria. Hofer (1890) found in a large 

 number of experiments that the removal of the nucleus exerted a 

 direct influence upon the movement of the protoplasm, and he 

 therefore concluded that the nucleus is a regulatory centrum for 

 the locomotion of the amoeba. He also found that enucleated 

 amoebse ceased to form the secretion wherewith amoebae attach 

 themselves to the substratum. His descriptions and figures 

 show that at no time did the fragments free from nuclear influence 

 approach normal locomotion. Willis (1916) observed a number 

 of enucleated amoebae for seventy-two hours. He observed that 

 during this time their movements were jerky, irregular and very 

 much slower than those of nucleated parts. They were able to 

 attach themselves to the substratum only weakly and for short 

 intervals of time. Lynch (1919) found that the enucleated part, 

 seven minutes after amputation, ceased its progressive move- 

 ments and retracted into a corrugated sphere. After one or two 

 days some of the nucleated fragments commenced to move 

 characteristically, but were not able to attach themselves to the 

 slide. Against all this evidence, we have the work of Stole (1910) 

 who reaches the rather amazing verdict that enucleated amrebae 

 show the same characteristic movement as nucleated ones, in- 

 cluding the feature of attaching themselves to the substratum. 

 Furthermore, he showed to his own satisfaction that enucleated 

 amoebee were as irritable as nucleated ones, and exhibited the 

 same stimulated condition. 



It is evident that it is impossible to gain from the literature 

 any adequate conception of the bearing of the nucleus upon the 



