158 G. L. Kite 



PARAMECIUM 



The living substance of Paramecium is a soft, elastic and somewhat 

 glutinous gel which can be drawn out into strands. It is filled with a 

 large number of vacuoles of various sizes the walls of which are more 

 dense than the surrounding gel. The surface layer is more viscous and 

 cohesive than the interior. Small cuts usually close quickly, exten- 

 sive deep cuts are either followed by a loss of cytoplasm or a rapid 

 change of the whole cytoplasm into the sol state with almost explosive 

 violence. If the fluid in the contractile vacuole be caused to mix 

 with the cytoplasm a rapid change of this substance into the sol state 

 results. Suspended in the living and apparently homogeneous and 

 rather dilute gel are varying numbers of extremely small granules 

 and small globules. Many of the granules are recently ingested 

 bacteria. Neither the granules nor globules go into solution when 

 dissected free from the cytoplasm. The food masses are granular 

 gels of rather high viscosity. 



The optical properties of the meganucleus render its study ex- 

 tremely tedious. It is almost transparent and invisible. Therefore 

 its refractive index and its dispersion are very close to those of water. 

 Dissection has proved the meganucleus to be a gel of higher viscosity 

 than the cytoplasm and to be slightly glutinous and elastic. The 

 meganuclear gel has areas, more dense than the surrounding sub- 

 stance, that may be considered granules. 



A complete study of the micronucleus has not been made. 



NECTURUS 



The Striped Muscle Cell. The. living substance of the striped 

 muscle cell of Necturus is the most viscous, elastic and cohesive of 

 the living gels we have so far considered. The muscle substance 

 sticks to a glass needle and can be drawn out into extraordinarily long 

 threads which when released almost regain their previous shape. 

 The absorptive power and turbidity of this substance are compara- 

 tively high. 



When the whole or a piece of a muscle cell is stretched the stria- 

 tions become faint or disappear only to reappear when the tension 



