MOLLUSCA. 7 



Teacher. They have not red blood as we have ; 

 but are they composed entirely of solid matter ? 



Child. No, for when a snail is trodden upon, 

 a white fluid issues from it ; is this its blood ? 



Teacher. Yes, it may be considered as a kind 

 of blood. How does it differ from that which 

 circulates through our bodies ? 



Child. It is white and cold. 



Teacher, True ; and in consequence some 

 naturalists have not considered it as blood, and 

 have described the mollusca to be exsanguineous ; 

 a term signifying, without blood, and derived from 

 Latin ex, out of, and sanguine, blood. However, 

 as this fluid flows through their bodies in vessels 

 issuing from their hearts, it is considered to be 

 their blood. What are you watching in the snail ? 



Child. The very quick manner in which it 

 draws in its horns, and shrinks into its shell, if 

 touched. 



Teacher. What would you determine with re- 

 spect to the animal from this circumstance ? 



Child. That it has the sense of feeling. 



Teacher. And which part appears most sensi- 

 tive? 



Child. The horns. 



Teacher. Do you observe how the little ani- 

 mal feels about with these projections which you 

 call horns ? They have from thence been termed 

 Tentacula, from the Latin, tentare, to try or feel. 

 How many tentacula have snails ? 



Child. Four. 



