VITA L PO 1] ER OF MO VI NG. 2 o I 



filament which it spins off behind it as it moves on ; in the 

 last, the tissue already formed is pushed on by the produc- 

 tion of new texture in its rear. The extremity of the hair 

 is its oldest part, and nearest to its root is the tissue which 

 was most recently formed. But whether bioplasm moves 

 on in its entirety, or, advancing from a fixed point, forms a 

 filament, a tube, or other structure which accumulates 

 behind it ; or remaining stationary itself, the products of 

 formation are forced onwards in one direction as they are 

 accumulate, or outwards in all, the nature of the force 

 exerted is the same, and due to the marvellous power which 

 one part of a living mass possesses of moving in advance of 

 another portion of the same, as may be actually seen to occur 

 in the humble amoeba, in the simple mucus-corpuscle, or in the 

 white blood-corpuscle, as well as in the pus-corpuscle formed in 

 disease. 



Amoeba. Among the simplest living things known to 

 us are the amoebae, which might be almost described as 

 animate masses of perfectly transparent structureless matter. 

 Amoebae, PI. Ill, figs. 3, 4, can be obtained for examination 

 by placing a small fragment of animal or vegetable matter in 

 a little water in a wine-glass, and leaving it in the light part 

 of a warm room for a few days. I have found it convenient 

 to introduce a few filaments of cotton wool into the water. 

 The amoebae collect amongst the fibres, and are thus pro- 

 tected from pressure when the thin glass cover is applied 

 and pressed down firmly so as to have only a very thin 

 stratum of liquid for examination. 



The delicate material of which these simple creatures 

 are composed, exhibits no indications of actual structure, 

 although it is undoubtedly somewhat darker and more 



