CELL-MULTIPLICATION IN A SPECIES OF ENTEROMORPHA. 557 
produce such extraordinary forms as those represented in figs, 18 and 19, where 
green shoots are seen as if arising from a colourless frond. 
The co-existence of two distinct kinds of cell being admitted, it is desirable 
next to ascertain the process by which these arise. With the green cells there 
is no difficulty ; their multiplication by transverse division is obvious ; but it is 
by no means easy, without the examination of avast number of specimens, 
to satisfy oneself as to the mode of origin of the colourless cells, or rather 
of that droplet of hyaline protoplasm (fig. 11) from which the colourless cell 
originates. 
The cellulose of an Alga is, as has been known from the time of Ktrzine 
and RABENHORST, no mere structureless investment, but possesses a capsular 
structure, quite similar to that which is so easily seen in Glwocapsa, or to that 
which has been demonstrated in the matrix of hyaline cartilage. This structure 
is shown in figs. 2 and 3, particularly well in the latter. Its origin is obvious ; 
a cell throws out a coat or shell of cellulose, and then divides into two new 
cells ; each develops its own investment of cellulose, and these lie end to end 
within the first. The extremities of these new cells being biconvex, they are 
thus not in complete apposition, but an angular interspace is left, which extends 
ring-fashion round the filament. Any irregularity of form or growth in the cell 
produces a corresponding irregularity in the disposition of the cellulose, and 
thus too in the form of the intercellular space, perhaps suppressing it on one 
side and enlarging it at the other. 
It is not to be expected that these lamine of cellulose should be of precisely 
equal thickness and strength throughout, nor of equal permeability to fluids. 
Where a weak place in the cellulose wall happens to come opposite the inter- 
cellular space, a certain amount of water might easily enter the latter from the 
cell; this water might soften and swell the circumjacent cellulose, and thus 
protuberances of the cellulose, and of the cellulose alone, such as those repre- 
sented at figs. 5, 6, 7,9, and 10, would easily arise. These phenomena are 
most probably to be considered as pathological. 
But if instead of a mere exosmose of water through the wall, we suppose 
the growing protoplasm itself to force a passage through the least resisting 
point in the innermost capsule of cellulose into the intercellular space, we have 
at once a reasonable explanation of the origin of the tiny drops of colourless 
protoplasm already described (fig. 11). Their position, almost invariably evenly 
intercalated between two given cells (fig. 7a), or at one side of the plane 
separating them (fig. 11); and their forms, biconcave and lenticular in the 
first case, hemispherical in the second, are strong proofs of their origin in 
this way. 
The cells at the bottom of the white shoots in figs. 2, 22, 23, 26, &c., are 
obviously each in an intercapsular space, and their protoplasm (which has in 
