66 
Wenham, on the Vegetable Cell 
that the primary contents are useless for the purposes of 
nutrition, I will merely mention that some recent and most 
valuable practical researches, made by an independent ob- 
server (and which I trust he will shortly bring before the 
public), have proved that extraneous matters may be conveyed 
into the mass of the formative plasma, and substituted for the 
contents of the primary cells, without interfering with the 
growth, and of such a nature as to afford no nutriment to their 
tissues. 
In conclusion I beg to inform the Society, that though the 
microscope has led me to take up particular views of cell 
development, 1 do not profess to write a complete essay on 
the subject. I will, however, remark, that it is still quite a 
new field for investigation, for all the controversies and con- 
tending theories that for years past have appeared on this 
theme have done but little towards the enunciation of a 
simple system of laws. As cell formation undoubtedly takes 
place, in various grades of complexity, the lowest and highest 
being widely different in their mode of production, in order 
to simplify this most important branch of science, I would 
venture to suggest, with all due deference, the possibility of 
classifying the subject, by arranging it in heads or depart- 
ments, or to make myself understood, say as follows : — 
1. Spontaneous appearance of membranous cavities in 
a primitive plasma, or simple differentiation. 
2. Cell formation by self-division, or the conjunction of 
definite membranes or utricles. 
3. Cells requiring special organs for their production. 
4. Allied phenomena, &c. 
If this were accomplished it would save some amount of 
confusion ; much of what is already known might be arranged 
under such heads as these. In the most highly organised 
plants, it is probable, that all these modes of cell formation 
separately exist, in various organisms. 
It is to after influences, or vascular bundles arising from 
the parent stem, that the proportions of symmetry and form 
are conveyed to the embryo cellular mass, dividing, distribut- 
ing, or increasing it according to its destined condition. At 
the time that these vessels and ducts begin to force their way 
through the young assemblage of cells, these differ so much 
in both individual form and arrangement, as to be typical in 
nearly all cases of the most excessive irregularity (the embryo 
leaves of the vine may be taken as an average example), and 
is utterly irreconcilable with the idea that the cavities or cells 
originate from the regular division and subdivision of pri- 
mordial cells. 
