I 12 



NEEDHAM. 



[VOL. I. 



original number of nuclei in the nidus, a fact sufficiently 

 accounting for their disappearance. Within the nidus at the 

 right of Fig. 6, the cells are more numerous than in those nidi 

 within the area from which the secretion has entirely been 



given off. Compare 

 also Figs. 3 and 8. 



(5) So far as one may 

 judge, division within 

 the nidus takes place 

 with great regularity. 

 As new cells develop 

 at the base of the ni- 

 dus, the older ones are 



FIG. 9. Epithelium, six hours after feeding, showing newly 



formed cells reaching up to the surface, replacing those CTOWdcd Upward. The 



discharged, x 230. nucleus of each grows 



rapidly, and soon acquires a spindle-shaped cell body. When 

 preexisting cells are not being used up in the digesting of food, 

 the young ones thus formed grow slowly, and making their 

 way upward against the compression of the older cells, are 

 crowded into crescentic form. But they continue to increase, 

 nevertheless, as a glance at Figs. 2, 3, and 4 shows. But 

 when the presence of food occasions the removal of the sur- 

 charged older cells, the increase in size of the 

 younger ones is remarkably rapid. Just before 

 a discharge, Hermann's fluid blackens all the cells 

 except the spherical ones immediately within the 

 nidus : just after, it leaves several cells on each 

 side entirely clear : and the inference is that these 

 cells have sprung up during that short interval, 

 the lateral compression of the older cells being 

 removed by their discharge, and have attained FIG _ A dis 

 their growth but have not yet become functional. 

 Fig. 9 shows the young cells apparently in the 

 act of crowding their way to the surface. The N> x 24 

 blackened area represents all that remains of the part that was 

 functional before the last discharge. The clear area consists 

 of cells that were uppermost in the nidus, but which have sud- 

 denly grown up to adult and functional proportions. If this 



sociation, show- 

 ing the constitu- 

 tion of the nidus 



