KEJUVENESCENCE 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. 



3. 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, 1 shall 

 give a somewhat detailed account of it, as I 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^rs^ stage, introducing the formation 

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

 appearance of the starch-grains. The mucilaginous layer 

 («'. 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. 



