225 
ON THE SPH^ROSIRA VOLVOX OF EHRENBERGL 
By Professor WILLIAMSON, F.R.S. 
[PLATE LXI.] 
W HEN the well-known aphorism of omne vivum ex ovo was 
displaced by the more recent one of omne vivum ex cellulo , 
it was thought, by many advocates of what has long been called 
the cell theory, that physiologists had reached the most ele- 
mentary form of organisation. But how far this is from being 
true is shown by the vast advance in knowledge of the subject 
which has taken place during the last twenty years. We 
have learned that what was thought to be the all-important 
cell is now but a comparatively insignificant product of the 
true generating organism ; an incidental portion which may or 
may not be present, but the presence or absence of which has 
little, if any, influence upon the active protoplasmic element 
in which resides the true life, and by which is fulfilled the 
important functions of growth and reproduction. The outer 
cell membrane resolves itself mainly into a mere framework, 
secreted by the active protoplasm, and designed to provide a 
suitable protective chamber in which the chemical and physio- 
logical operations of the protoplasm can be conducted without 
disturbance from external forces. Beyond this protective 
function, it is doubtful if the cell-membrane fulfils any 
purpose save that of the membranous analyser regulating 
some of the osmotic phenomena of which all cells are the 
seat. The true phenomena of cell-life reside in the proto- 
plasm, and if there is any truth in the doctrine of pan- 
genesis, we may yet have to fall back upon the minute 
granules which abound in protoplasm as the true repro- 
ductive germs, endowed with a self-sustained vitality, and 
capable, under certain circumstances, of an independent life 
and action. 
Since physiologists arrived at these conclusions many of 
the difficulties attending the study of the microscopic algae, 
once so formidable, have disappeared like the dew before the 
YOL. IX. — NO. XXXVI. Q 
