On the Structure of Amceboid Protoplasm, fyc. [Feb. 12, 



at present be decided. The same remark may be made with respect 

 to the question of active participation by the spongioplasm in the pro- 

 duction of the movements of the hyaloplasm. It is, however, quite 

 r.-rt-iiu from the observation of the movements of the hyaloplasm of 

 psendopodia, which may actively flow in different directions, even 

 when far removed from the spongioplasm, that it is the hyaloplasm 

 which is to be regarded as the physically active part of protoplasm, 

 and therefore also presumably of muscular substance. 



Lastly, there is another form of protoplasmic activity, viz., ciliary 

 motion, which cannot be left out of consideration in any attempt to 

 explain the manner in which the contractile manifestations of proto- 

 plasm are produced. On this matter I have no new facts to record, 

 and the suggestion therefore that I have to make must be under- 

 stood to be a purely theoretical deduction from analogy, and not] 

 based upon actual observation. At the same time it does not, so 

 far as I know, stand in contradiction to any known fact, 

 suggestion is briefly this : If we suppose that a cilium is a hollow 

 curved extension of the cell, occupied by hyaloplasm, and invested by 

 a delicate elastic membrane, then it must follow that if there be aj 

 rhythmic flowing of hyaloplasm from the body of the cell, into 

 out of the cilium, an alternate extension and flexion of that pi 

 would thereby be brought about. The movement would in fact be] 

 produced by an action which would be practically the same as that 

 by which the amoeboid movements of cells and the contraction and 

 extension of muscle are probably effected. The same result might be 

 got, supposing the cilium to be a straight and not a curved extension oi 

 the cell, if the enveloping membrane were thicker (or otherwise less . 

 extensible) alorg one side than along the other. This assumption 

 would also enable one better to account for the spiral direction of 

 the movement of certain cilia ; for this form of movement would be 

 produced if the line of lessened extensibility in them were to pass in 

 a corkscrew fashion along the cilium in place of straight along one 

 side, as might be assumed for ordinary cilia. 



