REJUVENESCENCE IN NATURE. 215 



swarming condition in April of last year. The large, 

 dark green swarmers, differing from other similar green 

 swarming cells by the remarkable truncation of both 

 ends, multiplied for some time longer, and here and there 

 produced very minute, paler and more brownish-yellow 

 microgonidia ; in the course of a few weeks no more 

 active cells could be found in the water, the full-grown 

 swarmers having all gradually come to rest and sunk to 

 the bottom. The originally longish shape of the cells 

 had changed into a perfect sphere with the transition to 

 rest ; the colour of these resting-cells, originally still green, 

 now gradually passed into a light yellowish-brown, at 



applied membrane (not standing away from the contents) of the old swarming 

 cells ; also by the absence of the little starch-vesicles in the interior, while, 

 however, as is usual in most of the Palmellacese, a single large " chlorophyll 

 utricle" (starch-utricle?) exists in the interior. There is no central red 

 nucleus, as in the gonidia of CUamidococcm, but some species have a parietal 

 red spot (an "eye"). The motion is effected by two cilia, as in Chlamido- 

 coccus. As in that genus, there is a growth of the gonidia during " swarm- 

 ing," which lasts over the day and night. There is also a formation of 

 microgonidia. The species of this genus are doubtless very numerous, but 

 the distinction of them among themselves, as well as from the swarming- 

 cells of many other Algse, is very difBoult without a complete acquaintance 

 with the history of their lives. The new species mentioned, CM. obtusa, 

 occurs in the Rhine valley, near Freiburg, in sand-pits, which are occasion- 

 ally almost completely dried up in summer. The macrogoiiidia grow during 

 their period of swarming, from ^ to almost ^ millim. long; they are 

 longish, of equal diameter on both sides, and very obtuse, almost truncated, 

 having a colourless place at the ciliated extremity, presenting the form of a 

 notch. In regard to other points, the contents are dark green, iinely 

 granular, with a large vesicle at the posterior extremity, a roundish lighter 

 space in front of this, and no red point. They multiply by simple or double 

 halving in several successive generations. Sometimes a further continuation 

 of the division of the fuU-growu macrogonidia occurs, forming sixteen or 

 thirty-two macrogonidia from ^ to yjj millim. long, of ovate shape, and lighter 

 colour, tending towards brownish-yellow. The resting (seed-) cells are 

 globular, about -^ millim. in diameter, at first green, subsequently light 

 yellowish-brown, finally flesh-red ; they have a tough, colourless, and trans- 

 parent membrane. Another species, CM. tingens, occurs in enormous 

 quantity in the puddles of the sandstone quarries at Lorettoberg, near 

 Freiburg, in the month of March, in mild seasons sometimes even in 

 January and February. The swarming cells are smaller than in the pre- 

 ceding, 755 to ^ millim. long, ovate, lighter green, likewise destitute of a 

 red spot, and the membrane is more distinct in the old age. Increase by 

 double, rarely by simple halving, in the former case with decussating 

 sections. I have seen the formation of microgonidia in this species ^Iso, but 

 not minutely observed the resting stage. (See preface.) 



