RAND : NERVOUS SYSTEM OF LUMBRICID^, 147 



of the cut end of the worm. Figure 48 is from a mass of cells more 

 dorsally placed, and so near the end of the alimentary tract that its 

 epidermal origin is perhaps doubtful. No other cells in this phase 

 could be found in the preparation. 



Figures 49-51 show late telophases in the same group of cells from 

 which Figures 46 and 47 are taken. All of these cells show a peculiar 

 condition of the cell membrane. In Figure 49 the interzonal filaments 

 are constricted at the equator, and there is a distinct "Zwischenkorper." 

 An equatorial membrane has formed between the daughter cells. The 

 triangular clearer region on the deep side of the two cells can best be 

 interpreted as the space from which the mother-cell membrane has 

 receded in its constricting. In the daughter cell at the right there is a 

 narrow clearer space immediately about the interzonal filaments and 

 the chromatic mass. On the deep side this space is so sharply outlined 

 as to appear bounded by a membrane. In the cell at the left there is 

 something which appears like a faint membrane (»i6.') lying just within 

 the old cell membrane. 



In Figure 50 there is a remarkable doubling of cell membranes, and 

 in Figure 51 a well defined membrane (vib.') in each daughter cell 

 evidently corresponds to the membrane mh.' in Figure 50. Outside 

 each of these membranes in Figure 51 is a region corresponding to the 

 regions in Figure 50 enclosed by the membranes, mb. In Figure 51, 

 however, these two regions are indefinitely outlined. 



These conditions would force upon us the conclusion that a new cell 

 membrane is formed within the old membrane of each daughter cell, and 

 that the old membrane finally disappears. A search through the epi- 

 dermis of this animal failed to reveal other stages which would throw 

 any more light upon the question. 



A centrosome may be seen in the concavity of the chromatic mass in 

 the right daughter cell of Figure 50, and in the left daughter cell of 

 Figure 51. In the latter figure a distinct nuclear membrane is formed 

 about the chromatin. Figure 52 shows two sister cells from the same 

 region. The section is somewhat oblique to the surface of the epider- 

 mis. The nuclei have increased in size, the concavity still persisting. 

 In the cell at the right the concavity of the nucleus is filled by a dense, 

 finely granular mass containing the centrosome with some faint radia- 

 tions. The presence of the centrosome at so late a period in the history 

 of the young cell is evidence that the central granule of the radiating 

 system of the resting cells (Figs. 44 and 45) is a true centrosome, 

 remaining from the last mitosis. 



VOL. XXXVII. — NO. 3 5 



