VIIl] 



THE SEGMENTATION OF THE EGG 



601 



the cell- walls met together in equihbrium. I suspect that a leaning 

 towards Sachs's Rule, that one cell-wall tends to set itself at right 

 angles to another cell-wall (a rule whose strict hmitations and 

 narrow range of apphcation we have already considered) is responsible 

 for many inaccurate or incomplete representations of the mutual 

 arrangement of associated cells. 



In the accompanying series of figures (Figs. 248-255) I have set 

 forth a few aggregates of eight cells, mostly from drawings of 



Figj 248. Segmenting egg 

 oiTrochus. After Robert. 



Fig. 249. Two views of segmenting egg of 

 Cynthia partita. After Conklin. 



Fig. 250. [a) Section of apical cone of Salvinia. After Pringsheim *. 

 [h) Diagram of probable actual arrangement. 



segmenting eggs. In some cases they shew clearly the manner in 

 which the cell-walls meet one another, always by three-way junctions, 

 at angles of about 120°, more or less, and always with the help of 

 five intermediate boundary walls within the eight-celled system; 

 in other cases I have added a slightly altered drawing, so as to shew, 

 with as Httle change as possible, the arrangement of boundaries 



* This, like many similar figures, is manifestly drawn under the influence of 

 Sachs's theoretical views, or assumptions, regarding orthogonal trajectories, coaxial 

 circles, confocal ellipses, etc. 



