PLANTS AND ANIMALS. ii 



animal the demands of locomotion and alimentation are 

 best satisfied by a maximum bulk with minimum surface, 

 whereas in a plant the absorptive area, being mainly co- 

 extensive with the surface, the typical plant tends to attain 

 minimum bulk with maximum surface. With such a large 

 proportion of surface there is no necessity for excretory 

 organs. 



Lastly, from the difference in food it follows that a plant 

 can, from the simplest to the highest, protect its body in 

 a supporting membrane, usually of cellulose, whereas an 

 animal must always have a certain part of its surface 

 exposed to form an ingestive and egestive area. When, as 

 in low types, the ingestive area is co-extensive with the 

 surface {cf. Amceba)^ the difference in this respect from a 

 plant is very marked. We may tabulate these differences 

 as follows : — 



PLANT.'' 



1. Protoplasm has chlorophyll. 



2. Food liquid or gaseous. 



3. No alimentary organs nor 



excretory ; motor and sen- 

 sory organs little developed. 



4. Form tending to maximum 



surface with minimum bulk. 



5. Body completely clothed in 



coat (cellulose). 



6. Are dependent on salts, car- 



bonic acid gas, water and 

 sunlight. 



ANIMAL.* 



1. No chlorophyll. 



2. Food solid, and mostly in- 



soluble. 



3. Alimentary and excretory ; 



motor and sensory organs 

 highly developed. 



4. Form tending to maximum 



bulk with minimum surface. 



5. Body naked in lowest types, 



partially enveloped in exo- 

 skeleton in higher. 



6. Live only upon plants or 



other animals (highly or- 

 ganised food), and do not 

 require sunlight or carbonic 

 acid. 



The plant-nutrition is sometimes termed holophytic and animal- 

 nutrition is then known as holozoic. 



Transfer of Energy. — The movements of animals, 

 and the maintenance of a high temperature in the higher 



* Ftmgi form an exception to I and 6 in the ^^Flant^^ column, 

 whilst Hydra and a few other animals form an exception to i in the 

 ^''AniinaV^ column. One or two plants are partial exceptions to 3. 



