ZYGOSPOREJE. 
disappear. Some minutes after the commencement of conjugation the resulting 
zygospore is a spherical cell {VI), which remains at rest for some time enclosed in 
its cell-wall, its green colour passing over into a brick-red. If the dried-up zygospores, 
which have now greatly increased in size, are placed in water, germination begins 
after twenty-four hours ; the outer shell of the cell-wall breaks up, an inner membrane 
protrudes and now contains one, two, or three large zoospores which finally escape 
{Fill, IX), surround themselves, after a short period of swarming, with a gelatinous 
envelope, and break up by successive divisions into sixteen primordial cells which 
now again form a coenobium like Fig. i. 
A further illustration of the course of development in the Pandorineae is furnished 
by Stephanosphcera plwvialis, one of the rarest and most beautiful of the family (Fig. 168), 
occurring rarely in the rain-water which collects in the hollow of large stones. 
The process of vegetative reproduction is the same as in Pandorina; but, according 
to Cohn and Wichura, the succession of generations of this kind is interrupted by 
the cells belonging to a family dividing repeatedly (Fig. 168, XII) into zoogonidia 
which ultimately become free {XIII), and probably produce resting zygospores by 
Fig. 168.— Successive stages in the reproduction oi Stephanospliara plnvialis {after Cohn and Wichura). 
conjugation after the manner of Pandorina. It is stated by the observers above-named 
that stationary immotile balls (/) accumulate at the bottom of the water which, as they 
grow, assume a red colour. After these resting-cells, which are probably zygospores, 
have lain for some time dry and then again been moistened, they germinate, the contents 
breaking up into from 4 to 8 zoospores {II— V) which invest themselves with a cell- 
wall, and each gives rise, in a single day by successive division {VII — IX), to an 
eight-cell ccenobium {X, XI), which again in the next night gives birth to eight 
motile families^. 
2. The nearest allies to the Pandorinese are probably the HYDRODiCTYEiE, as is 
shown by their formation of ccenobia, and still more by the whole course of their de- 
velopment, which Pringsheim^ first described in detail. Although the conjugation of 
the zoogonidia has in this case also not been actually observed, they offer a striking 
^ [Archer has described, /. c, pp. 7, 8, a remarkable amoeboid phase which the primordial cells 
of StephanosphcBra undergo.] 
^ Pringsheim, Mon. der königl, Akad. der Wiss. zu Berlin. Dec. 13, 1860. [Ann. des Sc. 
• Nat. i860, vol. XIV; Quart. Journ. Micr. Sc. 1S62, pp. 54, 104. See also A. Braun, Verjüngung, 
p. 146 ; Ray Soc. Bot. and Physiol. Mem. 1853, pp. 137, 190, see ajite, p. 251.] 
