6 LESSON I. 



various kinds from the general fluid of the sub- 

 stance. Animals as well as vegetables, are sup- 

 plied with a great number of glands ; the tears 

 of animals are an example of a secretion formed 

 by means of such organs ; so is the honey of 

 plants. As the glands form little reservoirs, they 

 often appear like small swellings, perceptible to 

 the sight and touch. Now can you tell me what 

 glands are ? 



Child. They are organs by which are secre- 

 ted some particular fluid from the general fluid 

 of the body. 



Teacher. To return to the mantle ; it some- 

 times envelops the mollusk like a purse, leaving 

 an opening only where its mouth is situated ; 

 sometimes it extends on the two sides, forming 

 expansions which perform the part of fins ; some- 

 times it spreads over the shell itself, which in 

 this case has always a fine polish. Compare, as 

 I desired you, the mollusks, with other animals, 

 and tell- me what further peculiarity you discover 

 in them. 



Child. They have no bones, their bodies are 

 only a mass of soft flesh. 



Teacher. They have certainly no bones ; but 

 in the mollusks 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 



