DEVELOPMENT OF CHARA. 319 



and if iodine be applied at this time, the division is seen 

 to 1)0 confined to the protoplasm, as the latter, from con- 

 traction, withdraws itself from each side of the Ime 

 where the septum appeared, and leaves a free space which 

 is bounded laterally by an uninterrupted continuation of 

 the protoplasmic sac. In this way changes go on until its 

 shape is altered and it becomes converted into a bunch 

 of rootlets. Thus the new cells are never entirely with- 

 out a nucleus, w'hicli would appear to exert some influ- 

 ence upon their development, for as soon as the only two 

 new cells which the root-cell gives off are formed, the old 

 nucleus becomes effete. 



" Now as to the office of the nucleus, nothing more is 

 revealed to us in the development of the roots of Chara, 

 than that, so long as new cells are to be budded forth, 

 the nucleus continues in active operation, but when this 

 ceases it becomes effete ; while the rotation of the pro- 

 toplasm and subsequent enlargement of the cell, &c., 

 "which are much better exemplified in the plant-stem than 

 in the root-cell, go on after the nucleus ceases to exist. 

 Hence the development of the root-cells of Chara affords us 

 nothing positive respecting the functions of this organ ; 

 and therefore, if we wish to assign to it any uses in par- 

 ticular, they must be derived from analogy with some 

 organism in which there is a similar nucleus whose office is 

 known. If for this purpose we may be allowed to 

 compare the nucleus of Chara with that of the rhizo- 

 podons cell, which inhabits its protoplasm, we shall 

 find the two identical in elementary composition ; that 

 is, both consist at first of a ' nuclear utricle,' respec- 

 tively enclosing a structureless homogeneous nucleolus : 

 the latter, too, in both, is endowed with a low degree of 

 movement. 



" After this, however, the nucleolus of the Rhizopod cell 

 becomes granular and opaque ; and when, under circum- 

 stances favourable for propagation, a new cell- wall is 

 formed around the nuclear utricle, — or this may be an 

 enlargement of the nuclear utricle itself, — I do not knovr 

 which : the oranular substance of the nucleolus becomes 

 circumscribed, and show^s that it is surrounded by a sphe- 

 rical, capsular cell j the granules enlarge, separate, pass 



