186 ANIMALS AND PLANTS. 



arrive at such organisms as the Psorospermice and the 

 Panhistopliyton, 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 com- 

 plex nitrogenous substance, pepsin ; the probability that 

 the Peronospora is nourished directly by the protoplasm 

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

 recently been brought to light respecting insectivorous 

 plants, all favour this view ; and tend to the conclusion 

 that the difference between 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. 



