656 THE POPULAR SCIENCE MONTHLY. 



ous witli a tube, which serve as mouth and gullet, but the food in- 

 gested takes a definite course and refuse is rejected from a definite 

 region. Nothing: is easier than to feed these animals and to watch 

 the particles of indigo or carmine accumulate at the lower end of the 

 gullet. From this they gradually project, surrounded by a ball of 

 water, which at length passes with a jerk, oddly simulating a gulp, 

 into the pulpy central substance of the body, there to circulate up one 

 side and down the other, until its contents are digested and assimi- 

 lated. Nevertheless, this complex animal multiplies by division, as 

 the monad does, and, like the monad, undergoes conjugation. It 

 stands in the same relation to Heteromita on the animal side, as Co- 

 leochcete does on the plant side. Start from either, and such an in- 

 sensible series of gradations leads to the monad that it is impossible 

 to say at any stage of the progress. Here the line between the ani- 

 mal and the plant must be drawn. 



There is reason to think that certain organisms which pass through 

 a monad stage of existence, such as the Myxomycetes^ are, at one time 

 of their lives, dependent upon external sources for their proteine-mat- 

 ter, or are animals, and at another period manufacture it, or are 

 plants. And, seeing that the whole progress of modern investigation 

 is in favor of the doctrine of continuity, it is a fair and probable spec- 

 ulation though only a speculation that, as there are some plants 

 which can manufacture proteine out of such apparently intractable min- 

 eral matters as carbonic acid, water, nitrate of ammonia, and metallic 

 salts, while others need to be supplied with their carbon and nitrogen 

 in the somewhat less raw form of tartrate of ammonia and allied com- 

 pounds, so there may be yet others, as is possibly the case with the 

 true parasitic plants, which can only manage to put together materials 

 still better prepared still more nearly approximated to proteine 

 lantil we arrive at such organisms as the Psorosper'mi(B and the Pan- 

 histopliyton^ which are as much animal as vegetable in structure, but 

 are animal in their dependence on other organisms for their food. 



The singular circumstance observed by Meyer, that the Torula of 

 yeast, though an indubitable plant, still flourishes most vigorously 

 when supplied with the complex nitrogenous substance, pepsin ; the 

 probability that the Peronospora is nourished directly by the proto- 

 plasm of the potato-plant ; and the wonderful facts which have 

 recently been brought to light respecting insectivorous plants, all 

 favor this view ; and tend to the conclusion that the difterence be- 

 tween animal and plant is one of degree rather than of kind ; and that 

 the problem, whether, in a given case, an organism is an animal or a 

 plant, may be essentially insoluble. Macmillan's Magazine. 



