REJUVENESCENCE IN NATURE. 281 



Nageli* treats, in the section on free cell-formation, the 

 phenomena of abnormal cell-formation, which are observed 

 in decaying contents of old cells. The mode of formation 

 of these abnormal cells certainly agrees most of all with 

 the cases last discussed, but has the peculiarity that the 

 new structures escaping the solution and decay of the 

 rest of the cell-contents are incapable of development, or 

 only of abnormal development, descending into diseased 

 structures or pseudo-organisms. The character of these 

 abnormal cells is most varied and changeable ; especially 

 remarkable is the occurrence of globular, resting, spore- 

 like cells (e. g. in old Closteria)^ as also the appearance 

 of active, Infusorioid structures, which occur not unfre- 

 quently in the interior of decaying cells of green fresh- 

 water Algae (e. g. (Edogonium, Spirogyrd),\ and are dis- 

 tinguished from normal swarming-cells by their irregular 

 form, varying size, slower motion, and mostly brownish- 

 yellow contents, succeeded by hyaline, finely granular 

 mucilage. In Spliaroplea I have often seen such pseudo- 

 gonidia formed in the same cells with normal spores. 

 Abnormal structures of this kind have doubtless often 

 been confounded with the normal reproductive cells of 

 the Algae. The future will certainly unfold many in- 

 teresting phenomena in this hitherto little-worked field. 



In the preceding summary of the modifications in 

 which the process of Rejuvenescence of cells advances to 

 new constructions, we have seen division of the cells 

 occur as a very ordinary accompaniment of the recon- 

 struction, and this in manifold ways. With these pro- 



* ' Zeitschrift,' 1847, p. 24, t. iii, f. 1 3 (Bryopsis Balbisiamim.) (Ray 

 Society's transl., 1849, p. 98, t. ii, f. 13. A. H.) 



t Meyen, Pflanzen-phys.,' iii, t. 10, f. 24, (also figured by Focke, 

 'Physiol. Studieu,' pi. iii, f. 12. A. H.) 



% (See Pringsheim, on Spiroffyra, Transl. in ' Annals of Nat. Hist.,' 2d 

 series, vol. xi, p. 210. Also consult on this point Itzigsohn, 'Bot. Zeit.,' 

 1853. A. H.) 



