132 The Study of Animal Life PART n 



at the junctions of the strands, and with, in each cell, one 

 or more central and larger swellings, probably of a highly 

 specialised nature, called nuclei. The size of the meshes 

 varies, and they are filled " now with a fluid, now with a 

 more solid substance, or with a finer and more delicate 

 network, minute particles or granules of variable size being 

 sometimes lodged in the open meshes,, sometimes deposited 



FIG! 30 Adjacent animal cells showing the nucleus, the protoplasmic network, 

 and the bridges vitally uniting cell and cell across the intervening inter- 

 cellular substance. (From the Evolution of Sex ; after Pfitzner.) 



in the strands of the network. Sometimes, however, the 

 network is so close, or the meshes filled up with material so 

 identical in refractive power with the bars or films of the 

 network, that the whole substance appears homogeneous." 

 The only means we have of getting any further knowledge 

 of this arrangement is by staining it with various dyes, and 

 observing the effects of the dyes upon the various parts. 

 " Analysis with various staining and other reagents leads to 



