ALGLE : THEIR STRUCTURE AND MODE OF REPRODUCTION. 31 
of its whole protoplasmic substance. It bursts through the wall 
of the cell and becomes free as an ellipsoidal body (fig. 5 a 
and 6), one end of which is chlorophyll-green, and the other 
hyaline, the latter being crested with a tuft of cilia, by the 
vibration of which it is propelled rapidly through the water. 
When it comes to rest, the cilia disappear, at the end where 
they grew root-like processes are put out by which it attaches 
itself to a solid body ; it then clothes itself with a cell-wall, and 
developes in the ordinary way. 
The Zygnemece are often united with the (Edogoniese, 
Diatomaceae, and Desmidieae into the family of Conjugate. 
The family includes a considerable number of filamentous 
fresh-water algae which may be found in almost any drop of 
stagnant water, remarkable from the brilliant green of their 
chlorophyll, which is arranged in the most varied and beautiful 
forms of stars, plates, or bands, revealed under the microscope 
from the perfect transparence of their cell-walls. One of the 
commonest and most striking objects is Spirogyra longata 
(fig. 6), in which the bands of chlorophyll are arranged in the 
most beautiful spiral form. The Zygnemeae produce no motile 
swarm-spores, but ordinary resting-spores or zygospores by a 
process known as Conjugation, confined to the Conjugate and 
a few fungi, which may be considered as the simplest possible 
form of fertilisation, the two conjugating cells being alike in 
form and structure, and therefore not distinguishable as male 
and female. In Spirogyra the conjugation always takes place 
between the adjacent cells of two more or less parallel fila- 
ments. A preparation is made for it by the formation of lateral 
protuberances (fig. 6 a) which continue to grow until they 
meet. The protoplasmic body, or 44 endochrome ” of each of 
the two cells contracts simultaneously, detaches itself from the 
surrounding cell-wall, and assumes an ellipsoidal form. The 
cell-wall then opens between the two protuberances, and one of 
the ellipsoidal protoplasmic bodies forces itself into the con- 
necting channel thus formed ; it glides slowly through it into 
the other cell-cavity, and as soon as it touches the protoplasmic 
body contained in it, the two coalesce. After complete union the 
united body is again ellipsoidal, and scarcely larger, owing to 
the expulsion of water, than each of its two constituents sepa- 
rately. It clothes itself with a cell-wall, forming the body 
known as a Zygospore, which germinates after a period of rest 
of some months, and developes a new filament of cells. 
In the family Gonfervaceoe are included an enormous number 
of green fresh-water algae, found in all ponds and running 
water, reproduced by minute zoospores or metamorphosed 
joints. Besides the more ordinary forms, a number of others 
are doubtfully referred to this family, as Hydrodictyon , in 
