VOLVOCINE.E. 53 



the contents their reel colour, no further visible alteration takes place 

 BO long as they are kept in water. A dessication must take place before 

 a new cycle of generations can begin. Perfectly dry specimens placed 

 again in water ordinarily produce active gonidia the next morning. 

 Original specimens obtained in 1841 had retained their vital force during 

 a preservation of seven years in a herbarium. 



" In order to complete the main features of the picture of the alter- 

 nating generations of this multiform creature, I must notice that, in 

 addition to the described active generations (macrogonidia and micro- 

 gonidia) and the concluding generation, passing into the spore-like con- 

 dition of rest, there are other generations which, as compared with the 

 gonidinm-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 

 are here characterized 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 Chlamydococcus, as often as they are filled by 

 showers of rain. In cultivation in the house these vegetative genera- 

 tions are rarely observed, while in their native stations they certainly 

 occupy the most important place in the alternations of the various con- 

 ditions of life, as may be concluded from the thickness of the crusts 

 and membranes formed by such vegetative multiplication. The forma- 

 tion 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 quarter- 

 ing). 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 drawn out to nothing, rather 

 than regularly burst open ; it at length vanishes in some undistinguish- 

 able way, the daughter-cells meanwhile acquiring a tolerably thick, 

 closely applied cell membrane of their own. The division is repeated 

 many times in this way, and as the cells all remain in intimate contact, 

 first small families, but by degrees large conglomerates of cells are pro- 

 duced. The size of the single cells in these groups varies from '01 to 

 02 mm. ; their shape is not truly globular, but partly bounded by flat 

 surfaces, as results from the alternating divisions, according to the three 

 directions of space. Ordinarily the colour is light brown. If ignorant 

 of the rest of its history, one would be led by the form and mode of 

 division of the cells to regard these crusts as belonging to a Pleuro- 

 coccus. In the same crusts occur isolated large cells, loosened from 

 their connection with the others, perfectly globular in form, and appear- 

 ing to divide no more, but to have passed again into the condition of 

 resting spore cells. Tney are distinguished from the rest by their 

 darker contents and thicker cell membrane. Probably the return of 

 these to renewed resting vegetation takes place by a passage through 

 the series of active generations. Every shower of rain will wash away 

 these loose ripe cells of the crusts of Chlamydocnccus ; carried into 

 collections of rain water, they will soon produce the active brood, which, 

 returning to rest after a few active generations, settles on the margins 

 of the little puddles, and then recurs to the resting mode of vegetative 

 multiplication." 



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