ELEMENTS OF ENTOMOLOGY. 



THIRD BRANCH OF THE ANIMAL KINGDOM. 



ARTICULATED ANIMALS. 



LESSON I. 



GENERAL CONSIDERATIONS. Structure of Articulated Animals 

 Division of the Third Branch of the Animal Kingdom. 



CLASS OF INSECTS. Organization Metamorphosis Classi- 

 f cation. 



1. The third great division, or Third Branch of the Animal 

 Kingdom, includes all animals that are constructed on the same 

 general plan as insects. Their internal structure is essentially 

 different from that of animals belonging to any of the other three 

 branches of the animal kingdom ; and their external characters 

 are so decided and evident that it is almost always easy to 

 recognise them at first sight. 



2. They are termed articulated animals animalia articulata 

 because their body is divided into sections, and seems to be 

 composed of rings, placed in a contiguous series on a line with 

 each other (fig. 1). The extremities in many instances are also 

 formed in this manner. These rings are formed of portions of 



Fig. 1. SCOLOPENDRA. 



1. What description of animals are comprised in the third branch of the 

 animal kingdom ? 



2. Why are they termed articulated animals ? How are the rings 

 formed? Have articulated animals any skeleton ? 



2 (9? 



