NSTRUCTION. 



TYPES OF CONSTRUCTION. 79 



By this radial symmetry we are conducted toward the 

 Vegetable Kingdom. Thus in the higher Fungi the dis- 

 position of organs is as radiate as in Radiated animals. 

 In Mosses and Ferns there is a spiral arrangement of 

 leaves around the axis, which may be considered the 

 regular law of growth in the higher plants, although 

 sometimes obscured by special modifications. 



8. It is a popular error, fostered by the assertions of 

 certain Monistic writers, that the higher animals pass 

 through all the phases of lower life. This false notion is 

 based upon too strict an interpretation of Von Baer's gen- 

 eralization in Embryology, that " a heterogeneous or spe- 

 cial structure arises by gradual change out of one more 

 homogeneous or general." Every division of the Animal 

 Kingdom has its characteristic method of developing. 

 " The Vertebrate arises from the egg differently from the 

 Articulate ; the Articulate differently from the Mollusk ; 

 the Mollusk differently from the Radiate." *" Every 

 grand group early shows that it has a peculiar type of 

 construction. Every egg is from the first impressed with 

 the power of developing in one direction only, and never 

 does it lose its fundamental characters. The germ of the 

 Bee is divided into segments, showing that it belongs to 

 the Articulates ; the germ of the Lion has the primitive 

 stripe the mark of the coming Vertebrate. The blasto- 

 dermic layer of the Vertebrate egg rolls up into two 

 tubes one to hold the viscera, the other to contain the 

 nervous cord ; while that of the Invertebrate egg forms 

 only one such tubular division. The features which 'de- 

 termine the subkingdom to which an animal belongs 



, , _ * Ac-assiz. 



