54 



NATURAL HISTORY. 



[Lesson XI. 



148. T. What are these two families ? 



P. The ^bronchia setigera, provided 



with silky bristles, as the earthworm 



Fig. IS.* 



tribe ; and 2, the Abranchia nuda, or the 

 ^bronchia without bristles, such as the leech 

 tribe. 



C.I.XF.RAL QUESTIONS ON LESSON X. 



1. What is the name of the third great 

 division of the Animal Kingdom ? 



2. What are articulated animals ? 



3. How many classes of articulated 

 animals are there ? 



4. Describe the peculiarities of the first 

 class, and give examples of each order and 

 family? 



5. Why have the Annelides been se- 

 parated from the other classes ? 



b'. Is there anything peculiar in the 

 nervous system of the Articulata ? If so, 

 state the peculiarity. 



LESSON XL 



LINNJEUS classed the Crustacea, Aractmida, and Insecta together, under the general 

 name of Insects ; but other Zoologists have thought 

 proper to divide them. The second class of articulated 

 animals is, properly speaking, the crustaceous or hard- 

 coated animals. They have a great many genera and 

 species, articulated legs, respire by branchiae, or a kind 

 of gills, sometimes enclosed, and in other species 

 external to the shell ; the circulation is double, and 

 resembles that of the Molluscous animals; and the 

 nervous system is of two kinds, which will be noticed 

 in another Catechism. 



QUESTIONS. 



149. T. How are the Crustacea divided? 



P. Into the MALACOSTRACA and ENTOMOSTRACA. 



150. T. Describe the peculiarities of the former. 

 P. The shell of the animals is hard and calcareous; 



they have ten or fourteen legs, hooked at tlie tip ; and 

 some have fixed eyes, while others have theirs placed 

 on a moveable piece. 



151. T. What is there peculiar in the second 

 division ? 



p._The shell is slender, and generally in two parts ; 

 the eyes are fixed, and frequently there is only one 

 of these organs. The legs vary in number, have only 

 one hook at the extremity, and appear more suited 

 for swimming than anything else. 



d 



distributed 



* Fig. 18. ffirudo nflicinalis, or leech. 



t Fit. 19. A vertical longitudinal section of the common 

 lobtter (AstacHs marinus). a. mandibles and palpi ; b, the 

 otoinach ; c c, intestinal prolongation of the same ; d, the outlet; 

 e, the heart ; / g h i. a system of KI eat blood-vessels distributed to 

 19 -t the posterior portion of the animal ; kl m, great blood-vessels 



to the sternal or anterior aspect of the body; n n n, lobes of the liver. 



