TYPES OF CONSTRUCTION. 81 



of a fish, a beak for eating vegetable food, and a spiral 

 intestine to digest it. As it matures, the hind legs show 

 themselves, then the front pair, the beak falls off, the 

 tail and gills waste, lungs are formed, the digestive ap- 

 paratus is changed to suit an animal diet, the heart is 

 altered to the Reptilian type by the addition of another 

 auricle in fact, skin, muscles, nerves, bones, and blood- 

 vessels vanish, being absorbed atom by atom, and a new 

 set is substituted.* 



10. With the caution referred to in Sec. I we may pre- 

 sent an outline of the types of living forms. 



The most general and comprehensive type is that of 

 bioplasm, or living matter, described in Chap. II, and 

 characteristic of both animals and vegetables. The next 

 most comprehensive type of structure is that of Vegeta- 

 ble forms in which the bioplasm is invested, or, as it 

 were, imprisoned, in each of its component cells by a sac 

 of cellulose, or some analogous compound, (Chap. IV, 

 Sec. 5,) and whose most characteristic work, or peculiar- 

 ity, is its power of manufacturing albuminoid matter out 

 of simpler chemical elements. In Animal forms there 

 is no such cellulose investment, nor can they make albu- 

 minoid matter from inorganic elements. 



In the Vegetable Kingdom we may arrange organic 

 forms under the following general divisions, or principal 

 types: 



i.) PROTOPHYTES, or simplest vegetable forms, an- 

 swering to the Unicellular Alga. 



2.) THALLOGENS, which are a mere expansion of cel- 

 lular tissue, without complete distinction between stem, 



* Orton. 



