VOLVOCINE^E. 55 



GENUS 38. CHLAftXYDOHEONAS. Elirb. (1833.) 



Macrogonidia ovate or oblong-rounded, green, delicately 

 granulated, involved in a rather narrow hyaline tegument 

 frontal extremity very obtuse, or somewhat truncate, with a 

 contractile vacuole, and two cilia ; posterior extremity with a 

 large chlorophyllose vesicle, and with or without a red lateral 

 spot. Microgonidia arising from repeated division of the cytio- 

 plasm of the macrogonidia, oblong or ovate, numerous, pale 

 green or yellow, becoming brownish. Tranquil oospores glo- 

 bose, red or brownish, contents firm, colourless, hyaline. 



" CMamydomonas is distinguished from Chlamydococcus by the closely 

 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 Palme ilacece, a single 

 large ' chlorophyll utricle ' (starch utricle ?) exists in the interior. 

 There is no central red nucleus, as in the gonidia of Chlamydocoecus, 

 but some species have a parietal red spot. The motion is affected by 

 two cilia, as in Chlawi do coccus. As in that genus, there is a growth of 

 the gonidia during ' swarming,' 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 them- 

 selves, as well as from the swarming cells of many other Algas, is very 

 difficult without a complete acquaintance with the history of their lives. 

 The species Chi. obtitsa, occurs in the Rhine valley, near Freiburg, in 

 sand pits, which are occasionally almost completely dried up in summer. 

 The macrogonidia grow during their period of swarming from '016 to 

 almost '033 mm. 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, finely 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 divi- 

 sion of the full-grown macrogonidia occurs, forming sixteen or thirty- 

 two macrogonidia from '005 to '008 mm. long, of ovate shape and 

 lighter colour, tending towards brownish yellow. The resting cells are 

 globular, about '025 mm. in diameter, at first green, subsequently light 

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

 transparent membrane. Another species, Chi. tingens, occurs in enor- 

 mous 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 

 preceding, '008 to '016 mm. long, ovate, lighter green, likewise destitute 

 of a red spot, and the membrane is more distinct in the old age. In- 

 crease by double, rarely by simple halving, in the former case with de- 

 cussating sections. 



" Several species of this genus, previously included in the animal 

 kingdom, but nearly allied to Gl&ococcus and Chlamydococcus, present 

 themselves in the beginning of spring, in such abundance that they 

 produce a striking green colouration of the water ; a few weeks later 

 they vanish, leaving no trace, and are not noticed again throughout the 

 whole vear." Braun Rejuvenescence, p. 215. 



