THE PHYSIOLOGY OF CELL-DIVISION we 
be true it might be expected that weak solutions of anaesthetics 
could be substituted for hypertonic sea-water. Experiments now 
being conducted (June 1911) indicate that this is in fact the 
ease with starfish eggs. Loeb has found chloral hydrate—a 
typical anaesthetic—to have an action on the eggs of Strongyl- 
ocentrotus, after artificial membrane-formation, similar to that 
of potassium cyanide.?° This fact accords with the foregoing 
interpretation. My experiments of this summer (1911) are at 
present too incomplete for further description. 
THEORETICAL 
According to the view put forward in the present and preceding 
papers alterations in the permeability of the limiting membranes 
of the cell are events of critical importance in the process of 
cell-division. An important controlling or directive réle is thus 
ascribed to the membranes; it remains to consider more fully the 
manner in which changes in the permeability of these structures 
can be the condition of changes so extensive as those concerned 
in cell-division and development. 
Development in all cases involves the transformation of a 
quantity of inert or non-living material into the characteristically 
organized and active adult animal or plant. It is thus largely 
a matter of definitely directed constructive metabolism. Since 
mitotic cell-divisions are intimately associated with the develop- 
mental process in all metazoa, one of the first steps in the investi- 
gation of the physiology of development must be to determine the 
nature of the metabolic processes in mitosis and of the conditions 
controlling them. 
be assumed. Thus Arenicola larvae brought from sea-water into pure isotonic 
NaCl solutions contract strongly, while at the same time the cells rapidly lose 
pigment. If, on the other hand, the organisms are brought from sea-water into 
isotonic magnesium chloride or sulphate solution, all contraction ceases and the 
animals remain rigid and extended, with no sign of muscular movement or loss of 
pigment; i.e., a typical anaesthetic action is seen. If the larvae, after an interval 
of some minutes, are then transferred to pure NaCl solution, no contractions, or 
at most very slight ones, result and there is no loss of pigment. In other words, 
the susceptibility to stimulation and increase of permeability is greatly decreased 
by the magnesium salt. The same is true of chloroform and ether in appropriate 
concentrations. 
20 J. Loeb: Chemische Entwicklungserregung, p. 70. 
