2 LoBBj on Micrasterias Denticulata. 



This is followed by the incision of the central and basal 

 lobes, and the central lobes being considerably larger than 

 the basal the whole assumes somewhat the appearance of 

 being composed of seven lobes. (See fig. 5.) 



After this a further incision of the central and basal lobes 

 takes place (see fig. 6); then the sinuation of the end lobes, 

 and the denticulation of the whole completes the division (see 

 fig. 7) ; then separation follows. 



In each stage the endochrome increases, but never extends 

 throughout ; the hyaline portion becomes less, the frustule 

 is gradually filled, and when self-division is completed, there 

 still remains a perfectly hyaline portion all round the cell. 



The figure in Mr. Ralfs's work represents the first 

 exudation from the parent frustules as very large, and 

 filled with a light colouring matter of the same density 

 throughout, leaving no portion hyaline. There is no divi- 

 sion into lobes, no incision, no denticulation, no granular 

 endochrome ; and all these are so natural, and so perfectly in 

 keeping with the parent frustules, that I do feel justified in 

 differing even from so high an authority, and am compelled to 

 say, that if ever such a self-division was witnessed, it must 

 have been an abnormal one. Having seen many frustules in 

 the course of self-division, and on different occasions, I 

 can with confidence assert, that I have never seen any devia- 

 tion from the method now descriljcd : there is a slight varia- 

 tion in the spreading of the endochrome, which, it shoidd 

 be observed, is always granular. 



The self-division only requires to be witnessed, to show 

 that what I have stated is correct; and, should any one 

 observe the phenomenon from its commencement to its close, 

 as I have done, he will, with me, assert that a more beautiful 

 object can hardly be seen even by a microscopist. 



There was one object which struck me very forcibly, on 

 looking over the gatherings from Epping Forest, and Avhich I 

 have endeavoured to figure, magnified only seventy-five dia- 

 meters. It differs, in several respects, from Actinophrys sol, 

 though there is some resemblance, both in its circular figure 

 and in the rays that issue from the disc; the central disc 

 is perfectly hyaline, excepting the cell-walls, the cells of 

 the inner disc being larger than the cells (if I may so 

 term them) of the outer disc. It may, or it may not, be 

 new, but I have never seen it figured. 



