Wen HAM, on the Vegetable Cell. 
65 
rudimentary walls, or rather septa, become one uniform and 
continuous solid — the true cell wall is still formed in the 
interior of each cavity, with the appearance of being moulded 
upon the mass of contents, and when the membrane has 
acquired consistency, the proper cell constituents arise within, 
from external absorption as in former instances. The cells 
may now be washed out from the intervening plasma in 
which they are imbedded, as separate sacs just in the same 
way as I have described before. 
The expanding action of the living protoplasm, may be 
seen in actual operation during the conjugation of the 
DesmidiecB — a process that I have always watched, with never- 
failing interest. When the two masses of endochrome are 
ejected, they are not bounded by any limitary membrane as 
some seem to suppose, but unite at first oftentimes in the 
form of a rugged mass. All the intervening protoplasm now 
separates from the general mixture, and forms an external 
sheath, which hardens into a membrane — the cell wall of the 
unicellular sporangium.* I bring this forward again, because 
the expansive effect of the protoplasm, as seen to take place 
here, will illustrate the action in the associated cells in 
question, when filled with contents, by considering each cell 
in the formative plasma for the time being, as a separate and 
independent organ. 
If now one system of cells are first formed with empty 
cavities, and another with more or less of primary contents, 
the question arises, what ought to be the physiological differ- 
ence in favour of the subsequent vital welfare and develop- 
ment of the latter ? As far as my investigations have gone I 
cannot say that the full cells appear to differ much in growth^ 
or derive after benefit from the circumstance of their first 
replete condition, the well-doing of the cell still depending 
upon external conditions ; but without going so far as to state 
structure, there seems to be a beautiful combination of this vital action, in 
conjunction with definite chemical arrangement, or a crystallization of the 
calcareous deposit, giving rise to very regular and perfect cellular forms, 
and prismatic structures. It would be a very interesting inquiry to ascer- 
tain how far these two forces act together in harmony, in forming regular 
cell arrangements in other departments of the animal and vegetable king- 
dom. This would be an investigation in which the polariscope would be 
extremely serviceable. 
* In some of the Desmidiece and Algce, when the endochrome or con- 
tents of one cell are forced out, by the application of gentle pressure, into 
the water, the first action is somewhat similar to that which takes place 
during conjugation. The protoplasm separates from the other consti- 
tuents, and is determined outwards as a complete envelope, the mass ac- 
quires a spherical shape, and remains so for many hours, but no consis- 
tent exterior membrane is ultimately formed ; all vital action ceasing at 
this point, the mass always proving barren. 
