228 C. M. CHILD. 



the gradient is reversed, is probably due to the greater area be- 

 tween the cells which is a very general characteristic of the 

 new parts developing under these conditions. The cell turgor 

 is apparently less than under normal conditions, and the young 

 cells therefore depart more or less from the spherical or ovoid 

 form characteristic of young cells produced under normal con- 

 ditions, and in consequence of this change the surfaces of con- 

 tact become larger and separation occurs less readily. 



Figs. 11-14 show other cases of development of isolated cells 

 from Osterhout's culture, in which the susceptibility gradients 

 were not determined. In Fig. II two new apical cells arise from 

 the original basal end, and a rhizoid from the original apical end 

 of the cell. In Fig. 12 a new axis of two cells has developed 

 from the basal end of a group of two cells, and rhizoids appear 

 at various levels on the old cells. In Fig. 13 the two ends of the 

 old cell apparently develop independently of each other, each 

 giving rise to a new axis and a rhizoid at approximately right 

 angles to the original axis, and a third rhizoid appears in the 

 middle region. Fig. 14 shows a somewhat similar case with a 

 two-celled axis and two rhizoids developed from the apical 

 region of the old cell and a one-celled axis from the basal region. 

 It will be noted that in all these cases the new apical cells arise 

 at or near one or both ends of the old cells. Among all the 

 cells examined, both from Osterhout's and from my own cul- 

 ture, only one case was found (Fig. 15) in which a new apical 

 cell arose from the middle region of the old cell. This case was 

 returned to the culture after examination in the hope that 

 further development would occur, but could not be found later. 

 Numerous other cases of development occurred in the isolated 

 cells of these two cultures, but those described give a fair idea of 

 the variety of axial relations observed. 



DISCUSSION. 



If the axial susceptibility gradient is in any degree an indica- 

 tion of the general metabolic relations along the axis, and if 

 these metabolic relations are effective factors in determining the 

 axial order or pattern, then the apical cell represents the region 

 of highest metabolic rate, and in the vigorous axis under good 



