REJUVENESCENCE IN NATURE. 211 



to the described active generations (macrogonidia and 

 microgonidia) and the concluding generation passing into 

 the spore-like condition of rest, there are other gene- 

 rations which, as compared with the gonidium-like and 

 spore-like conditions, must be regarded as the proper 

 representatives of the vegetative development. These 

 are generations endowed with quiet and slow vegetative 

 growth, which multiply by pure vegetative division, 

 unaccompanied by any swarming movement. It depends 

 solely upon external conditions whether the resting-cells 

 which I have characterised as seed-cells (spores), at once 

 give rise to the new active generations, or to a series of 

 quietly vegetating generations of cells. The former is the 

 case when the seed-cells are totally immersed in water ; 

 the latter when they occur on a spot which is at once 

 damp and exposed to the air,* as is the case in the 

 native condition, especially in the milder intervals of 

 winter and in the damp season of approaching spring, 

 but temporarily also, at all other seasons, on the margins 

 of the little basins inhabited by CMamidococcus as often 

 as they are filled by showers of rain. In cultivating it 

 in the house, I have but rarely observed these vegetative 

 generations, while in the native stations they certainly 

 occupy the most important place in the alternations of 

 the various conditions of life, as may be concluded from 

 the thickness of the crusts and membranes formed 

 by such vegetative multiplication.! The formation and 

 multiplication of these vegetative generations also take 

 place by the division of the cell-contents, either by simple 

 division, the first generation being transitory, or by 

 double halving (apparently quartering). But the newly 

 formed cells do not slip out, like the young " swarmers/' 

 from the mother envelope ; they remain in the same place 

 and position. The membrane of the mother-cell appears 

 to become softened, expands, and becomes gradually 



* Probably in such cases no perfect dessication takes place, 

 f Heematococcus pluvialis, var. leprosus, Von Flotow, 1. c. 



