no HOURS WITH NATURE. 



could not have failed to notice that it has a distinct 

 head with a mouth, and a pair of short broad " lips," 

 which in Zoological language are called " mouth tenta- 

 cles ;" also that it has a pair of long wire-like head 

 tentacles, upon some part of which the eyes are 

 placed. Have you ever attempted touching one of 

 these snails while slowly and deliberately crawling 

 along ? What has been the result ? It quickly retires 

 into its house or shell. Here is an opportunity for you 

 to study the other parts of a snail from this dissected 

 specimen. The body is enveloped in a fold of skin 

 which is called its " mantle ;" the under part of the 

 body is thickened to form an elongated solid foot for 

 progression; the thin-walled upper part contains the 

 viscera and is permanently placed within the cavity of 

 the shell. The internal organs of a typical mollusc 

 consist of (i) an alimentary canal, coiled and embedded 

 in a dark digestive gland or liver ; (2) a two-chambered 

 heart; (3) an excretory organ or kidney; (4) the re- 

 productive gland ; (5) the nerve-ganglia placed in front 

 of the alimentary canal ; (6) the salivary gland. Another 

 characteristic organ of a typical mollusc is the "tongue," 

 or " odontophore," as it is called by the Zoologists. 

 It is a horny strap, of which the upper surface 

 is generally covered with small sharp teeth-like projec- 

 tions arranged in rows like a rasp. When not used, 

 it lies coiled up on the floor of the mouth, but when 

 in use it acts backwards and forwards like a saw." 



