342 
POPULAR SCIENCE REVIEW. 
And this brings me to the last fact to wbicli I wish to draw 
attention. These gonidia can continue for an indefinite period 
in the same mode of growth to which they have passedj while 
the external conditions remain the same. 
Now this is an important fact, because it strikes at the force 
of the argument which considers the apparent fixity of the 
Palmellacege as an evidence of their separate entity. It shows 
the necessity for these studies of enlarging the field of our 
researches j of expanding our comprehension of the variabihty 
of nature ; and of continuous patient careful observations. 
Any one looking for the first time at the plate to Cohn^s 
paper on Protococcus pluvialis, translated in the Pay Society's 
work, 1853, will be astonished at the very diverse forms which 
he has traced from the simple cell, which was considered till 
that time to form its whole existence. What a field then, in 
all probability, remains for future observers, endowed with an 
equal amount of industry. The reason so many disputes con- 
cerning the animal or vegetable nature of Yolvox and many 
other organisms have arisen, has been from the want of con- 
tinuing the observations on their mode of growth for a longer 
time ; as well as from our want of collateral knowledge of the 
development of similar plants. 
Let us then extend our researches in this direction, let us 
determine our species and genera rather by their mode of 
growth than by their particular form, seen only for a short 
time or under similar conditions ; a great opportunity is here 
for many investigators, one which will not be exhausted for many 
years. The whole of the Confervoids require to be thoroughly 
gone through in their modes of growth under varying condi- 
tions. This is a task not attractive to some; but to the 
patient intelligent observer it will yield far more satisfaction, 
a deeper insight into nature^ s ways, and a greater expansion of 
the mind, than can ever be obtained by the mere seeking for 
species. 
DESCEIPTION OF PLATE XIV. 
Fig. 1. Chlorococcus in different ''stages of division. — 2. Sori of Lichen 
opened, showing the green cells or gonidia. — 3. Cells of same in a state 
of division. — 4. Simple cells of Prasiola, dividing in various manners. — 
5. Confervoid filaments of Mosses, throwing off cells. — 6. Ditto, ditto, 
which are dividing in various ways. — 7. Gleocapsa. — 8. Green cells of 
Cup-moss, producing cells like Gleocapsa and Pahnoglea. — 9. Ditto, 
ditto. — 10. Green cells of Confervoid filaments of Mosses, producing 
forms like Gleocapsa. — 11. Palmoglea. — 12. Protococcus iridis, pro- 
ducing Zoospores (6). — 13. Cells of Moss, producing Zoospores {a). 
N.B. — Figs. 7, 11, and 12, are drawn on rather too large a scale ; they 
should he same size as those with which they are compared. 
