REGENERATION OF PROTOPLASMIO FRAGMENTS 507 
according to which the throwing out and the drawing in of 
the pseudopodia are attributed to changes in surface tension. 
This theory is based on the assumption that the pseudopodia 
are liquid.’ This assumption is a physical impossibility. 
The pseudopodia of Orbitolites are, according to the 
drawings of Verworn, cylindrical; their length perhaps a 
hundred times greater than their circumference. Such a 
liquid cylinder cannot exist. There is a good reason why 
rain falls in drops and not in jets. If r is the radius, h the 
height of a liquid cylinder, it can exist only as long as 
h=2rm, For this reason alone the entire contraction theory 
of Verworn is wrong. I will not, however, discuss this theory 
more closely here.” From these facts in surface tension it 
follows that the pseudopodia of the Rhizopods cannot be 
liquid, but must possess a solid framework or a solid mem- 
brane. Assoonas this solid framework or the solid membrane 
becomes liquefied the pseudopods must obey the laws of 
surface tension and break up into drops. The latter is, 
according to my observations, the process which occurs in 
fragments of Orbitolites which contain no nucleus. 
Is this liquefaction of solid substances a process which is 
indicative of lack of oxygen? This is undoubtedly the case. 
Four years ago I showed that the cell-walls of the cleavage 
cells of Ctenolabrus become liquid when deprived of oxygen. 
When oxygen is readmitted, the formation of cell-walls 
begins anew.’ Budgett showed in my laboratory that the 
removal of oxygen leads to the solution of the cell-walls in 
Infusoria also, and that certain poisons had the same effect.* 
Kuhne has observed the same effect of lack of oxygen.’ The 
1 Die Bedeutung der lebendigen Substanz (Jena, 1892), p. 38. 
2I do not here mention the chemotropic ideas of Verworn because they rest 
upon no actual foundation whatsoever. 
3“Investigations on the Physiological Effects of Lack of Oxygen,” Part I, 
p. 370. 
+ American Journal of Physiology, Vol. I (1898). 
5 Zeitschrift fiir Biologie, Vol. XXXVI (1898), p. 472. 
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