CONDITION OF AGGREGATION OF ORGANISED STRUCTURES. 
or barium nitrate, but permeable to potassium chloride or water. Traube considers 
that in the permeability of the pellicle-precipitates we have a means of determining the 
relative size of the molecules of different solutions, since only those molecules can pass 
through the pellicle which are smaller than its micellar interstices and therefore smaller 
than the molecules of the solutions which produce it. 
If a small quantity of ammonium sulphate is added to a solution of ß gelatine, and a 
small quantity of barium chloride to one of tannic acid, and the two mixtures thus 
obtained are themselves mixed, a pellicle is formed of gelatine tannate, and in it a 
precipitate of barium sulphate which diminishes the size of the interstices ; the two 
solutions which cause the deposit can no longer diffuse ; but the incrusted pellicle is still 
permeable to the smaller molecules of ammonium chloride and water. 
Traube maintains that there is no such thing as an endosmotic equivalent in the 
sense of the older theory. Endosmose is independent of any interchange, since it 
results entirely from the attraction of the soluble substance for the solvent; and this 
attraction is invariable at any given temperature and may be termed Endosmotic Force. 
The endosmotic force of grape-sugar, for instance, is very great, that of gelatinous 
substances very small. 
To these researches, which are of extreme importance in reference to vegetable 
physiology, and of which we shall make much use in the sequel, though with a cautious 
selection, Traube has added observations on the growth of the pellicle-precipitates of 
copper ferro-cyanide, the main results of which however I have been unable to confirm 
after a number of experiments. 
If a drop of a very concentrated solution of copper chloride is dropped into a 
dilute solution of potassium ferrocyanide, it immediately becomes coated with a thin 
brownish pellicle of copper ferrocyanide which exhibits peculiar phenomena. tt is 
more convenient to place small pieces of copper chloride in the ferrocyanide solution, 
where a green drop is immediately formed at the expense of the water of the solu- 
tion, producing the pellicle on its surface, and still enclosing the solid copper chloride 
which dissolves gradually from the permeation of the water. These cells manifest active 
growth and a variety of differences not easy to explain and dependent on secondary 
circumstances. Some have very thin pellicles, are roundish, and exhibit a slight tendency 
to grow upwards ; they usually form a number of small wart-like outgrowths and attain 
very considerable dimensions (from i to 2 cm. in diameter) ; they appear to be formed 
chiefly by the solution of large pieces of the copper chloride. Others have thick reddish 
brown pellicles, grow quickly upwards in the form of irregular cylinders, rarely branch, 
and attain a diameter of from 2 to 4 mm. and often a height of several centimetres. 
Combinations of the two forms also occur which sometimes form a kind of horizontal 
tuberous rhizome-like structure from which long stalk-like outgrowths arise upwards, 
and root-like protuberances downwards. 
It is impossible, in the space at our disposal here, to give a detailed description 
of these phenomena ; one only may be specially mentioned : — that these pellicles of 
copper ferrocyanide do not grow, as Traube supposes, by intussusception, but in quite 
a different way (by eruption). When a brown pellicle has been formed round the green 
drops, water penetrates quickly from without through it to the copper chloride ; 
the pellicle becomes rapidly stretched, and, as may be clearly seen, at length ruptured. 
The green solution immediately escapes through the fissure, but becomes at once coated 
with a pellicular precipitate which appears either as an intercalated piece of the previous 
one, or as an excrescence or branch of it, a process which is repeated as long as any 
copper chloride remains inside the cell. We cannot therefore in this case conclude 
that deposition of fresh micellae of the pellicle takes place between those already in 
existence. These cells cannot, so to speak, be injured; if they are pricked, then at 
the moment when the point which pricks them is withdrawn an outgrowth follows 
immediately, which is easily to be explained from what has been said. In conse- 
quence of the rapid flowing in of water through the perforation, the dissolved or the 
