44 PROTOPLASM. 



moves first, and the molecules flow into the extended portion. 

 The movements cannot, therefore, be ordinary molecular 

 movements. It has been said that the movements may result 

 from diffusion, but what diffusion or other movement with 

 which we are acquainted at all resembles these ? Observers 

 have ascribed them to a difference in density of different 

 parts, but who has been able to produce such movements by 

 preparing fluids of different density ? But further, in the case 

 of the living matter, these supposed fluids of different density 

 make themselves and retain their differences in density. 



Nor is it any explanation of the movements to attribute 

 them to inherent " irritability," unless we can show in what 

 this irritability essentially consists. Some dismiss the 

 matter by saying that the movements depend upon the 

 property of " contractility," but the movements of germinal 

 matter are totally distinct from contractility, as manifested 

 by muscular tissue ; since they take place in every direction, 

 and every movement differs from the rest, while in muscular 

 contraction there is a constant repetition of changes taking 

 place alternately in directions at right angles to one 

 another ; and hence, if the movements in question be due 

 to contractility, it is necessary to assume two very different 

 kinds of contractile property.* 



The movements in the mucus corpuscle and in the amoeba, 

 are of the same nature as those which occur in the germinal 

 matter of many plants, as is easily observed in the cells of 

 the leaves of the vallisneria or the anacharis, in the chara, 

 and in the hairs of the flower of Tradescantia ; and the 



* See my paper "On Contractility as distinguished from purely 

 vital movements." "Trans. Mic. Soc." 1866. 



