76 THE CELL 



enveloped by a delicate lamella of oily substance, is exceedingly 

 doubtful. For if we only take into account the single fact that 

 protoplasm is composed of a great number of chemical substances, 

 which, during the metabolic processes upon which its life depends, 

 are continually undergoing chemico-physical changes, we cannot 

 but think that conditions much more complex in their nature 

 must be necessary for its movements, than those required for a 

 moving drop of saponified oil, and, indeed, the complexity of these 

 conditions must be proportionate to the immense difference in the 

 complexity of the chemical composition and organisation of the 

 two substances in question [cf. statements already made on this 

 subject on p. 22 ; and Die Beivegung der lebendigen Substanz by 

 Vervvorn (III. 24)]. Further, all the protoplasmic movements 

 the streaming movements, the radial arrangement round attrac- 

 tion centres, the movements of cilia and flagella, and muscular 

 contraction together constitute a single group of correlated 

 phenomena which demand a common explanation. This, however, 

 is not afforded us by the experiments of either Quincke or 

 Biitschli. The movements, induced by them in a mixture of sub- 

 stances, bear the same relation to the movements of living bodies, 

 as the structure of the artificial cell produced by Traube does to 

 the structure of the living cell. 



Fig. 42, which is taken from a paper by Verworn (III. 24), 

 shows what very different appearances, closely resembling the 

 various kinds of pseudopodic extensions, may be produced by the 

 simple spreading out of a drop of oil upon a watery solution ; a-d 

 is a drop of salad oil which has spread itself out upon soda solu- 

 tions of different degrees of concentration ; in a it has assumed 

 the form of Amoeba guttula, in b and c of Amoeba proteus, and in d 

 of a plasmodium of a Myxomycete. Figs, e and /, which repre- 

 sent drops of almond oil, resemble the formation of pseudopodia 

 in Heliozoa and Radiolaria, whilst g is taken from Lehmann's 

 Molecular Physics, and represents a drop of creasote in water, in 

 which it has assumed a form resembling a typical Actinosphzerium 

 (Verworn III. 24, p. 47). 



Other attempts to explain the protoplasmic movements (Engel- 

 mann III. 6, Hofmeister II. 20, Sachs) lead us into the domain 

 of theories upon the molecular structure of organised bodies, since 

 the cause of the movements is supposed to lie in the changes of 

 form of the most minute particles. A discussion of Verworn 's 

 latest attempt (III. 24) would lead us too far in another direction. 



