14 LESSON I. 



pansions which perform the part of fins. Some- 

 times it spreads over the shell itself, which in 

 this case has always a fine polish. Remember 

 I desired you not only to examine the mollusca, 

 but to compare them with other animals. What 

 further peculiarity do you discover in them 1 



Child. They have no bones, their bodies are 

 only a mass of soft flesh. 



Teacher. They have certainly no bones ; but 

 in the mollusca which we purpose studying, the 

 shell, by acting as a support to the body, seems 

 in some measure to answer the purpose of 

 bones. What more do any of you discover in 

 these animals ? 



Child. They do not appear to have any blood, 



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 1 



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 exsanguin- 

 eous ; a term signifying without blood, and 

 derived from Latin ex, out of, and sanguine, 

 blood. As this fluid flows through their bodies 

 in vessels issuing from their hearts, it is now 

 generally called their blood. What are you 

 watching in the snail ? 



