34 
POPULAR SCIENCE REVIEW. 
the male receptacle, presenting the appearance of a drop of 
viscous exudation. At the same time, the spores, surrounded 
by the inner membrane of the oogonium, are also expelled, and 
collect outside the mouths of the female receptacles. When 
they again come into contact with the water, the spores burst 
through this membrane, and at the same time the antherozoids 
escape from the antheridia. The antherozoids collect in large 
numbers round the spores, as represented in fig. 10 ; and the move- 
ment of their cilia is so energetic that they impart to the spore 
to which they are attached a rotatory motion, which lasts for 
about half an hour, finally coalesce with it, and thus ferti- 
lising it ; after which it finally comes to rest. A short time 
after these processes are completed, the fertilised spore or 
oospore surrounds itself with a cell-wall, fixes itself to some 
other substance, and begins, without any period of rest, to germi- 
nate, lengthening and dividing at the same time. This process 
may be followed under the microscope by placing together in a 
drop of water some of the spores and a small quantity of the 
viscous matter taken with the point of a needle from the mouth 
of the male receptacles. The entire field of the microscope 
may sometimes be seen covered with brownish spheres bristling 
with antherozoids, which roll themselves about in all directions 
under the influence of the vibratile cilia. 
3. The Floride^e or Rhodospore^e are almost invariably marine 
algse, a very few forms being found in fresh water ; they are 
generally of a rose-red, violet, or purple colour, often with leaf- 
like fronds, but very variable in size and in the consistence of 
their tissues. The various families cannot here be described 
seriatim , but one deserves special mention, from the peculiarity 
of its structure, viz. : — 
The Corallinacece or Corallines. From their external resem- 
blance to the coral-forming polyps, these substances were long 
supposed to belong to the animal kingdom ; but are now 
known to be algse which possess a similar power of extracting 
the carbonate of lime from sea-water. The lime may be 
removed by weak acid, and the nature of the true tissue 
revealed. They are reproduced by a vegetative process, by 
means of Tetraspores, no sexual organs of reproduction having 
hitherto been discovered. The common species, Corallina 
officinalis , grows everywhere between tide-marks, on rocks, &c., 
and presents a branched, mostly pinnate, tuft of articulated fila- 
ments evenly coated with carbonate of lime. 
Two distinct modes of reproduction occur in most families 
of Floridese, the asexual and the sexual. The first is distin- 
guished from that known in other families of algse by the fact 
that zoospores endowed with free spontaneous motion are never 
produced ; but in their place Tetraspores, which are perfectly 
