ELEMENTS OF CQyCHOLOGY. 



SECOND BRANCH OF THE ANIMAL KINGDOM. 



MOLLUSC A: 



MOLLUSKS, OR SOFT ANIMALS. 



LESSON I. 



GENERAL CONSIDERATIONS. Mollusca in general Organiza- 

 tion Nervous System General Form Skin Mantle 

 Shell Formation of Shell Digestive Apparatus Circula- 

 tion of the Blood Respiration Senses Eggs Classifica- 

 tion. 



The long series of vertebrate animals, the history of which we 

 have already concluded, forms only a small part of the animal 

 kingdom, and to make the beings we are now about to study as 

 interesting as the vertebrata, we should be obliged to very far 

 exceed the limits of these lessons : but these animals are less 

 useful to us ; they attract less attention, and most of them pass 

 unnoticed, except by those who are at the pains of becoming ac- 

 quainted with them ; their faculties are more limited and their 

 structure is less complicated and less perfect. 



1. All these lower animals want a spinal marrow and a true 

 internal skeleton ; this last character has obtained for them the 

 collective name of invertebrate animals ; but in a natural classi- 

 fication, they could not all be placed in the same group, because 

 they are evidently formed after three different types, and there- 

 fore should be divided into three distinct branches, namely : the 

 mollusca, the articulata^ the radiata, or zoophytes. 



2. The branch of zoophytes is composed essentially of the 

 most imperfect animals : according to the classification of Cuvier, 

 which we follow, this branch comprises a certain number of beings 

 which seem, in a manner, to present the first sketch of the mode 

 of organization proper to mollusks and articulate animals ; its 

 place is therefore among the lowest grades of the animal series, 

 and passes, by gradual shades, from the type of the radiate ani- 

 mal to that of the two great branches which spring from it. These 

 two latter branches, one equally with the other, present a con- 

 stantly increasing complication of organization, and form, as it 



1. What are inver'tebrate animals ? What groups or divisions include 

 the inver'tebrate animals ? 



2. What are zo'ophytes ? Why are the mollus'ca placed before the artlc- 

 ulata in the series of animals ? 



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