THE ZYGNEMACEiE. 
315 
always associated the idea of a complete whole, a concrete 
and not a discrete whole, and also the manifestation of 
independent life. We will then define as an individual any 
concrete whole manifesting life, or any concrete whole having 
a structure which enables it, when placed in appropriate 
conditions, to continually adjust its internal relations to 
external relations, so as to maintain the equilibrium of its 
functions. Thus we have to consider as individuals all buds 
and shoots of plants, each aphis, each single polype, &c. 
ON “ THE ZYGNEMACEiE: A CHAPTER IN THE 
HISTORY OF THE FRESH-WATER ALGiE.”* 
BY MR. F. BATES. 
The Zyynemaceai, an important and in¬ 
teresting family of fresh-water algae, occur in 
ponds, ditches, &c., as floating or partially 
submerged, unattached masses of a pale to 
a dark grassy-green colour, and are slimy to 
the touch. In their younger and sterile 
condition they are amongst the most beauti¬ 
ful of all the fresh-water algae, when viewed under the 
microscope in a freshly gathered state. Unfortunately they 
suffer considerable deterioration some time after being 
mounted as microscopic objects, as no trustworthy medium 
has yet been discovered which will preserve them in their 
pristine beauty, a certain shrinking, with loss of brightness 
and colour in the chlorophyll bodies, always ensuing. The 
masses consist of delicate, long threads or filaments, 
composed of rows of cylindrical cells. A marked feature in 
the larger and more robust species is the cytoblast or nucleus , 
which is suspended in the sap-cavity of the cell by means of 
delicate threads of protoplasm, radiating from it to the 
chlorophyll bodies ; but it is these latter which most attract 
attention by the beauty of their form, arrangement, and 
colouring. These bodies in Zyynema take a radiate, or 
stellate, form, a pair in each cell; in Spiroyyra they consist 
of longitudinal rows of parietal bands, arranged spirally; in 
Mesocarpus and others, of axile plates or bands. 
Ayamoyenesis, or vegetative increase, is effected in these 
plants by repeated transverse cell-division or bi-partition, 
with subsequent growth of each moiety to the dimensions of 
the original cell. 
* Transactions of Section 1) of the Leicester Literary and Philo¬ 
sophical Society. Read April 23rd, 1884. 
