REJUVENESCENCE IN NATURE. 261 



Chytridium (p. 185), in which genus the nuclei scattered 

 through the whole contents of the mother-cell, are clearly 

 distinguishable before the formation of the boundaries of 

 the gonidia. Perhaps the formation of the spores of 

 many Fungi, in particular the genus Erysiphe* belongs 

 here. 



2. The daughter -cells are formed by the division of a 

 mucilaginous layer coating the inside of the wall of the 

 mother-cell. Since this by no means very rare mode of 

 cell-formation to which the term " parietal cell-forma- 

 tion would seem apt, were it not already used in another 

 sense has never yet been acurately described, I shall 

 give a somewhat detailed account of it, as 1 observed 

 step by step in the formation of the gonidia of Hydro- 

 dictyon. I have already spoken of the strange mode of 

 reproduction of the Water-net (pp. 137, 222) ; and 

 the characters of the cell-contents (pp. 171, 197) and 

 the cell-membrane (p. 190), before the commencement 

 of reproduction, have also been explained; so that, 

 taking up the subject at that point, I may commence 

 immediately with the description of the phenomena 

 through which the beginning of the formation of gonidia 

 is announced. The first stage, introducing the formation 

 of the gonidia, comprises the period of solution and dis- 

 appearance of the starch-grains. The mucilaginous layer 

 (i. e. the more consistent, formative contents resting 

 against the cell-membrane, the subordinate divisions of 

 which have been described above, and which retain their 

 parietal position up to the completion of the formation of 

 the gonidia) changes its aspect in a remarkable manner at 

 this period. The fresh transparent green becomes more 

 opake, and the entire mucilaginous layer acquires, even 

 before the solution of the starch-granules is completed, a 

 peculiar, regular appearance, closely beset with lighter 

 spots, which appearance, however, is only distinctly per- 

 ceptible when the focus is adjusted to the bottom of the 



* See Corda, 'Icon. Fung.,' ii, t. xiii, f. 100. 



