836 THE POPULAR SCIENCE MONTHLY. 



Thus the green bodies of animals do not correspond with the chloro- 

 phyl-bodies of the algae, but are independent organisms, or one-celled 

 algae, which have been named zoochlorella. Yellow cells are found 

 living under similar relations in actinias and radiolarias, which have 

 been distinguished as zooxanthella. 



The physiological as well as morphological independence of the 

 green cells is also demonstrated by the fact that when separated from 

 the animals they continued to live in this condition for days and weeks, 

 and formed starch in the sunlight. When grafted upon hydras and 

 infusoriae, which were quite free from chiorophyl, they continued to 

 live upon them. 



The conclusion is drawn from these researches that self-formed 

 chiorophyl is wanting in real animals, and that, when it is present in 

 their bodies, it originates in plants that have immigrated to them. 

 The most interesting result from them is the answer they give to the 

 question as to the significance of the green and yellow algae to the 

 animals in which they occur. In order to examine this matter more 

 closely, colonies of radiolarii containing numerous yellow cells were 

 put into filtered sea-water. They not only continued to live in it, but 

 outlived the specimens that were left with the other organisms. Now, 

 since the radiolarii are real animals, incapable of living on any but 

 organic matter, while in this case air and water afforded them all 

 the support they required, they could have been kept alive only by 

 the yellow cells that lived upon them, working up the inorganic sub- 

 stances that were provided for them, under the influence of light, into 

 organic. Further experiments showed that fresh-water sponges could 

 be cultivated to the best advantage in filtered water, thus demonstrat- 

 ing that the zoochlorella and the zooxanthella are fully competent to 

 maintain the animals in which thev live. If the animals contain few 

 or no green or yellow algae, they are fed, like real animals, by the 

 assimilation of solid organic matter ; but, when they contain algae, 

 they may be fed, like real plants, by the assimilation of inorganic 

 matter. In the latter case, the algae living in animals perform pre- 

 cisely the same function as the chlorophyl-bodies of plants. 



-"- 



PEOFESSOE EUDOLF VIECHOW. 



PEOFESSOE EUDOLF VIECHOW is almost equally well known 

 as the leader of one of the principal German schools of scientific 

 thought and as a prominent actor in the field of German politics. In 

 the former capacity his name is inseparably associated with the theory 

 of cellular pathology, which he first expounded and which he has 

 maintained with eminent consistency ; in the latter character he has 

 gained an honorable fame as a faithful guardian of the municipal in- 



