414 Prof. H. Karsten on the Formation, 
cavities or vacuoles are formed, which separate the rest of the 
granular mucilaginous contents into two portions,—namely, a 
central portion surrounding the nucleus, and a peripheral one, 
lining the inner surface of the primordial sac; but the two are 
united by simple or branching fibres extending between them. 
In the cells of Cladophora no nucleus is visible. Their plasma 
is described as mucilaginous, of greater density at the surface 
contiguous to the second inner cell, where it contains much 
chlorophyll and starch (and, according to Nageli, hardens to 
form the inner sac [Innenschlauch]). The state of matters m 
this instance, however, is somewhat different; and a thorough 
discussion is necessary to enable us rightly to estimate the 
organization of these cellular plants, as also that of the plant-cell 
generally. : 
The contents of Cladophora glomerata, which escape when a 
section of the plant is made under water, are for the most part 
readily destroyed by the action of the water, so that only the 
corpuscles of chlorophyll and starch, and, at a later period, only 
those of the latter, can be discerned. These starch-vesicles 
frequently constitute the nuclei of the chlorophyll-grains, and 
advance in growth within them during the liquefaction of their 
substance. Further observation of the exuded substance of the 
wounded joint of the Conferva, whilst submitted to the action of 
water, will show that this apparently mucilaginous fluid consists 
of hyaline vesicles and cells, which are filled with a transparent 
liquid, either quite colourless or in part coloured by a greenish 
matter. The latter, where present, adheres like a green mucilage 
to the surfaces of the very delicate envelope of the cells, coats them 
externally or internally, and often entirely fills their cavity. The 
size of these vesicles varies from the most minute to others whose 
diameter considerably exceeds the transverse diameter of the 
Conferva. However, the determination of their original dimen- 
sions is very difficult ; for all of them, at the moment the section 
of the Conferva is made, and upon coming into contact with the 
water, undergo an extraordinarily rapid and considerable disten- 
tion, and mostly soon rupture. By causing movements in the 
water, the escaped delicate and yet unruptured cells may be 
made to roll and demonstrate the resistance to water which their 
membrane enables them for some time to maintain. Moreover 
similar delicate cells may be observed in the emptying portion 
of the cut joint-cell, adhering here and there to the inner surface 
of the secondary membrane. The central cavity of the joint-cell 
becomes eventually filled with water, or, it may be, with air, if 
the latter has been allowed to enter during the making of the 
section. 
Several small vesicles and thin-walled cells, of the same sort, 
