236 



HOFMKISTER, ON 



(by which gradual advance the broken, sharply-angular suc- 

 cession of these cells is converted into a spiral) but that 

 there is no perceptible divergence of the newly formed septa 

 of the cell of the first degree from the oldest opposite side 

 wall of this mother-cell. 



There is a second series of facts which militates not less 

 decidedly against the above assumption, viz., the occurrence, 

 although a rare one, of apical surfaces of cells of the first 

 degree which exhibit angles not corresponding with those 

 of the frond-arrangement. The following instances have 

 been observed, and they are the only ones obtained in a 

 long series of investigations : 



In the greater number of these irregularly shaped cells 

 their size is very remarkable. In none of the foregoing 

 tables did the base of the triangle attain the length of 

 64 m. m. m., a length which is here often surpassed. 



But the measurements of those apical cells in which the 

 length of the oldest side-wall considerably exceeds that of the 

 youngest, are very instructive. Taken in connexion with the 

 fact, that in by far the greater number of instances the 

 angles of the apical cell correspond with the divergence of the 

 frond-arrangement, these phenomena indicate that after 

 each division the apical cell does not become enlarged 

 equally in all directions so as to attain the size which it 

 had before the division, but that the expansion which 



