210 THE PHENOMENON OF 



of the rest were all green, except the little red nucleus, 

 or even often entirely green, now gradually become red 

 again, passing from green through many tints of brown, 

 or of brilliant golden green and golden brown, into red. 

 These globular, thick-coated cells (the same as those with 

 which we began) behave like seed-cells or spores, passing 

 into a state of perfect rest. They do not exhibit any 

 growth, and after the membrane has attained its proper 

 thickness, and the contents their red colour, no further 

 visible alteration takes place, so long as they are kept in 

 water. I have preserved them for several months in 

 water, without any new development taking place ; on 

 the contrary, they at length began to be bleached and to 

 die away, if they were not devoured by the rapidly 

 multiplying Rotifer {Philodina roseola). A desiccation 

 must take place before a new cycle of generations can 

 begin. This is the peculiarity to which I especially 

 wished to draw attention here. Even a short stage of 

 dryness renews the Rejuvenising power of the resting 

 cells, and this is retained for a great length of time in 

 the dried condition, as might be deduced from the mode 

 of occurrence of the plant, and may also be easily proved 

 by artificial experiments. Perfectly dry specimens placed 

 again in water ordinarily produce active gonidia the next 

 morning. I have made the most remarkable experiments 

 on this point, on specimens which Herr von Flotow was 

 kind enough to send me. Specimens gathered at Hirsch- 

 berg, in Silesia, in March, 1848, placed in water at 

 Freiburg in April of the same year, exhibited new-born 

 active young within 22 hours; specimens dried in 1846, 

 in about 32 hours ; finally, original specimens obtained 

 from the stone slab over the Froschgrabe in 1841, after 

 about three days' soaking. These last had therefore 

 retained their vital force during a preservation of seven 

 years in an herbarium.* In order to complete the main 

 features of the picture of the alternating generations of 

 this multiform creature, I must notice that, in addition 

 * See Von Plotow, in regard to this, 1. c, p. 500. 



