80 THE AMERICAN MONTHLY [March 



Protoccocus, or Volvox being considered as animals, but I 

 will maintain, and I take my stand on the observations 

 of very eminent botanists, that both in Spongilla and 

 Hydra the green color which is present, is due to the 

 symbiosis of small green algse with the sponge and polyp 

 in question. In these two animals the green color is con- 

 tained in the form of round green corpuscles. These 

 green bodies were formerly looked upon as equivalent to 

 the chlorophyll corpuscles of the flowering plants ; but it 

 has recently been shown that they are surrounded by a 

 vegetable cell wall, and finally Beyerinck was able after 

 overcoming many difiiculties, to cultivate them independ- 

 ently, and has thus proved that they are in fact small 

 green algse (to which he has given the name of Zoochlor 

 ella) living within the cells of the sponge or polyp. The 

 advantage to the animal is obvious. The small algse are 

 able to form starch and hence sugar from the carbonic acid 

 dissolved in the water, and this we know can transfuse 

 through the cell wall of the alga into the animal body. 



The only advantage that can apparently accrue to the 

 algse is the fixity of abode, an advantage one would not 

 have considered very important to so small a plant which 

 has so many free living allies. We cannot, however, at 

 present, fathom all the desires of these small unicellular 

 plants. 



In the case of some Turbellarians, according to Han- 

 stein, the ZoochlorellsB have undergone a degeneration 

 and have lost their cell wall, so that they are now quite 

 dependent on the animal and cannot be cultivated inde- 

 pendently. 



A perfectly similar case to the occurrence of green algse 

 in Spongilla and Hydra we find if we leave the animal 

 kingdom out of consideration altogether, and this points 

 to the fact that these small green algse lend themselves 

 very readily to such partnerships, or are very willing to 



