1916] Wilsuii: On tJtc Life-nistory of a Soil Amoeba 251 



stages (pi. 20, fig. 52), in a few stages of the metapha.se (pi. 20. fig. 48), 

 and usually may be seen in the earlier stages of the anaphase (pi. 18, 

 fig. 10; pi. 20, figs. 37, 42). In the later anaphase it is not usually 

 easily distinguished, because in most individuals the chromatic polar 

 masses are very dark. However both eentrioles and a portion of the 

 central spindle may be clearly made out in some instances (pi. 20, 

 fig. 37). 



The granules or eentrioles are generally within the chromatic polar 

 masses (pi. 20. figs. 37, 42, 48, 52), not at the tips of the caps nor in 

 the metaphase even within the chromatic polar ma.s.ses. but are, how- 

 ever, to be found on focusing down even in the region between the 

 polar mas.s and the chromosomes, but nearer the former (pi. 20, fig. 42). 

 The connection between them, the central spindle, stains a little deeper 

 than a spindle fiber, is slender, and during the stages in which the 

 karyosome is dumb-bell shaped is in the narrowed region of the divid- 

 ing karyosome. When the two polar masses are separated, it remains 

 as a connection between them (pi. 20, fig. 52), having, as previously 

 stated, changed its position from the periphery to the center of the 

 spindle. 



Some of the workers on amoebas hold that there is no centriole, 

 others that there is. Among these, Hogue (1914) figures "a structure 

 closely resembling a centriole in a few amoebas." Glaser (1912a) 

 says he occasionally finds a granule which is a part of the karyosome 

 and retains the stain longer than the remaining part, but that it is not 

 a centriole. Hartmann (1913) figures a centriole in Amoeba hyalina, 

 but in this species there are no polar caps. He (1914) also figures 

 eentrioles in A. lacertae, though Dobell (1914) says that they do not 

 occur in that species. Likewise Alexeieff (1913) says that there is no 

 centriole in the amoebas which he has studied. 



The preparations from which the drawings of the centriole were 

 made were stained by Dobell's alcoholic haematin method (1914) and 

 so the structures figured are certainly not the ' ' fortuitous appearances 

 which may occasionally be met with in Heidenhain preparations," as 

 he says in speaking of those described by Nagler (1909). They are 

 definite structures which behave as fixedly as the karyosome does. 



The peripheral chromatin or chromatin net is not very evident in 

 resting nuclei, the only indication of its presence being that the nuclear 

 membrane has a thick appearance (pi. 19, fig. 19). Chatton and 

 Lalung-Bonnaire (1912), in characterizing Amoeba Umax Dujardin. 

 say that there is "dans I'etrait peripherique compris entre la parai de 



