258 H. S. WILLIS. 



of which are usually small, are not formed alternately as they 

 are in the parts containing the nucleus. Neither do they always 

 occur near the anterior end. These differences in movement in 

 the two segments are illustrated in Figs. I and 2. 



The nucleated part represented in Fig. i formed pseudopods 

 within one minute after division. At three minutes it was 

 attached to the substratum and exhibited the coordinated 

 movement characteristic of a normal individual (Fig. i, a, b, c, 

 etc.). This fragment was observed every three to five minutes 

 for an hour, and the movement was found to be essentially the 

 same throughout the entire period. The enucleated part of this 

 individual on the contrary, became globular immediately and 

 remained so for approximately five minutes during which time a 

 number of small short pseudopods were directed outwards in all 

 directions from the body. These became fewer and larger, and 

 the entire body elongated in the direction of one of the larger 

 pseudopods. An attachment of the body to the substratum was 

 then formed and regular movement followed for about one 

 minute. There was no subsequent locomotion or "streaming 

 movement"; the organism, however, changed its shape by fre- 

 quent contractions of the cytoplasm. These changes continued 

 for an hour when the experiment was brought to a close (Fig. i , 

 1-3). Throughout the entire period, the movement in the 

 enucleated part was very much slower than that in the nucleated 

 part. 



Essentially all of these characteristic differences in the move- 

 ments of the two fragments in question are further elucidated in 

 the sketches reproduced in Fig. 2. By referring to this figure it 

 will be seen that there was considerable locomotion in the nu- 

 cleated part and that pseudopods were formed more or less 

 regularly on the opposite sides of the segment; while in the 

 enucleated segment there was extremely little locomotion and 

 pseudopods were formed irregularly. 



Figs, i and 2 are typical illustrations of the behavior observed 

 in all of the specimens studied forty in number. The movement 

 in all nucleated parts of these specimens was like that in normal 

 specimens and the movement in all enucleated parts was quite 

 different from that in normal specimens. The behavior of 17 



