MITOCHONDRIA IN PLANT AND ANIMAL CELLS. 223 



about a visible difference in the living cell independently of the 

 other, though in the majority of the cases they probably act 

 together. So that it is very difficult to tell whether the mito- 

 chondria are active or passive agents. 



The belief is gaining ground (Kingsbury, '12, p. 46; Mayer, 

 Rathery and Schaeffer, '14, p. 619, and others) that mitochondria 

 are concerned with respiration in animal cells; that is to say, 

 with the taking up of oxygen. This conception is based upon 

 the view that mitochondria chemically resemble phosphatids, it 

 being thought by some that phosphatids outside the body are 

 capable of auto-oxidation. It falls well in line with the very 

 wide distribution of mitochondria as well as with the funda- 

 mental nature of the process of respiration. And of course, the 

 same arguments apply to mitochondria in plant cells for plant 

 cells also take up oxygen. It seems that, in this particular, 

 there is no great difference between mitochondria in these two 

 great groups of organisms. 



Unfortunately it is not possible to transfer plant mitochondria 

 to animal cells to see what they would do, or vice versa. We are 

 working in the dark, but we have only ourselves to blame because 

 we have not taken full advantage of certain lowly protozoans, 

 like Euglena viridis and others, which have, confined in the scope 

 of a single cell, all the properties which we are prone to consider 

 distinctive of both plants and animals. They contain chloro- 

 phyll, produce paramylum, a carbohydrate resembling starch, 

 and at the same time engulf, devour and digest certain still more 

 minute organisms. The brief description of mitochondria-like 

 material in Euglena, made by Ternetz ('12, p. 463), would serve 

 as a point of departure. The planarian worm, Convoluta ros- 

 coffensis, which takes in algae and lives in symbiotic relationship 

 with them would repay further study. We have here an animal 

 containing animal mitochondria with all their attributes which, 

 after symbiotic relationship has been established, "ceases to 

 take in solid food and depends entirely upon its vegetable part- 

 ners" (Bayliss, '15, p. 295). Another opportunity is afforded 

 by Chlamydomyxa labyrinthuloides which when at rest lives as a 

 plant and when active like an animal (Parker and Haswell, '97, 

 p. 49). 



