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of most rapid growth. In the cleavage of the egg of Moniezia the 

 larger blastomeres contain more or less yolk and not infrequently 

 undergo mitosis ; but amitosis is the characteristic form of division in 

 the smaller blastomeres which contain no yolk and divide much more 

 rapidly. Various other data in support of this view occur in the 

 literature and will be discussed elsewhere. 



But amitosis often occurs where rapid growth is not taking place 

 though it appears usually to be associated with relatively intense 

 activity of some sort. It seems not improbable that in many if not 

 in all cases factors of the same general nature may be involved and I 

 desire to suggest that these factors may be connected with a scarcity 

 of nutritive material. It may seem at first glance a contradiction in 

 terms to postulate scarcity of nutritive material in regions of rapid 

 growth or secretion or other special synthetic processes, but I believe 

 such a scarcity is not only possible but probable: in the first place 

 it must be remembered that the character of cellular or nuclear acti- 

 vity is not necessarily determined merrly by the amount of nutritive 

 material available. This is evident from the fact that in certain organisms 

 growth and division do not proceed beyond a certain point no matter 

 how great the supply of nutritive material, as well as from the fact 

 that extensive growth and cell-division may occur during regulation in 

 starving animals (e. g. planariaus), where the nutritive material for 

 the new growth is derived from other organs and tissues of the body. 

 Here very clearly the nutritive material goes where the demand is 

 greatest and total atrophy of relatively inactive regions may occur. 

 Now there is good reason for believing that in regions of intense 

 cellular or nuclear activity the demand is greater than the supply, or 

 in other words a state of "hunger" exists and physiological equilibrium 

 is not attained. Orthodromic processes must be especially characte- 

 ristic of such a condition and amitosis is apparently associated with 

 such processes as was noted above. On the other hand, when the 

 supply of nutritive material equals or exceeds the demand a condition 

 of equilibrium will be reached and maintained, or else cyclical changes 

 on both sides of equilibrium will occur more or less rythmically. 

 Attention was called above to the probability that such cyclical changes 

 are apparently involved in mitosis. 



In short, I am inclined to believe that amitosis is associated 

 with conditions where the demand for material or perhaps for certain 

 substances exceeds the supply. The evidence is not sufficient at present 

 to warrant the unqualified acceptance of this suggestion and it may 

 be that other conditions also bring about amitosis; but I believe the 



