THE LIVING SUBSTANCE. 45 



markedly more refractive than the structured areas. While I 

 agree with Biitschli that we are often deceived, as in the in- 

 stance he cites, and which I have also verified, into believing 

 an area of protoplasm to be structureless because of a greater 

 tenuity, by stretching, of its alveolar lamellae ; I have seen 

 numberless times the origin from visibly structured areas, of 

 true, optically structureless protoplasm, by progressive sub- 

 division, or reduction, of the structure of Biitschli. This often 

 takes place with marvellous rapidity, and to a point of minute- 

 ness causing great difference of optical quality, and the area so 

 formed may be very fluid or markedly viscous. 



It is in no other way that the ordinary structureless portions 

 of ectosarc of Amoeba, etc., are formed. True, there are very 

 hyaline and delicately structured areas which arise without 

 such reduction, except near the periphery, by outflow from the 

 endosarc of interalveolar material, with or without fluid alveoli 

 of Biitschli's structure, but it is reduction phenomena which 

 give a veritable structurelessness of appearance. Both sets of 

 phenomena may be witnessed within a few moments in an 

 Amoeba radiosa which delights in varying its activities a thou- 

 sandfold. Even without any perceptible change of form in the 

 animal, which may at the time be somewhat rigidly extended 

 in the water in the form of a star, of four, six, or any moderate 

 number of arm-like rays, or spread out as a fan-shaped film ; 

 the structureless substance will in a variable time be resolved 

 again to a very marked structure of Biitschli, 



At both times, under sufficiently low powers, the ectosarc will 

 have an optical structurelessness, and possibly also a greater 

 refraction than usual ; yet in one case the structure of Biitschli 

 as such has been obliterated, and in the other case is again 

 present. The increase of refraction in the substance may be 

 seen to be caused by a change in quality of the interalveo- 

 lar material, so that the meshwork of Biitschli's structure stands 

 out refractively, as thickened trabeculae, under lower powers 

 than are usually needed to resolve it. Structural reduction in 

 the living substance does not always result in thinning the 

 interalveolar material. Pellicular and interalveolar material 

 furnish commonest instances of apparent optical structureless- 



