74 ' THE INFLUENCE OF INANIMATE SURROUNDINGS. 



living within it commensals or ' messmates,' as they are called. 

 Kleinenberg's observations on Hydra viridis are decidedly 

 favourable to the former of these views ; Schulze's statements 

 as to Vortex viridis are equally positive in favour of the 

 second. For he expressly declares that the chlorophyll bodies 

 of this worm are true cells, unlike those of plants ; that they 

 divide and multiply spontaneously, which the chlorophyll 

 bodies do not ; and finally that they are in some individuals 

 wholly wanting. The importance of these arguments is increased 

 by other facts. It is known that most of the Radiolaria in- 

 variably bear in their body certain peculiar particles known as 



FIG. 18. Collozmim inerme (Haeckel), a Badiolarian forming colonies, a, a colony; 6, 

 a solitary individual, or, more correctly, the internal vesicle of one (the shaded bodies 

 are globules of fat, the outer spots indicate the numerous yellow cells). 



the yellow cells (fig. 18), in which a few starch-grains are always 

 present. These yellow or sometimes green cells occur in many 

 fresh-water Radiolarians which have lately been often made the 

 subject of minute investigations. From these, above all from 

 the very careful labours of Cienkowsky, it has recently been 

 proved that these yellow cells in the Radiolarians are in fact 

 nothing more than one-celled Algae living as messmate? with 

 the animal in the same sort of community as certain Fungi and 

 Algae which, as is well known, combine to form the apparently 



