488 ANIMAL REPRODUCTIONS: 
* tail; and an extremely thin membrane covert 
* the under part, with which the {nail advances, 
* and is called the foot. In the middle are lon- 
* gitudinal lines, and on the fides tranfverfe ones, 
‘indicating the tendons of the mufcles below, 
‘ ferving for action and re-aétion. ‘This anterior 
* and extreme part of the foot contracts with the 
‘lower mandible, leaving a little vacuity, pro- 
‘ bably that the motions of the mandible may be 
* more free and quick. At the root of the {mall 
* horns are the lips ; and when thefe are opened, 
* the teeth, tongue, and cavity of the mouth, are 
‘feen. Under the right large horn, and perhaps 
“a little behind and near the foot, is obferved a 
‘ {mall white mark amidft the tubercles of the ~ 
¢ fkin, which is the female vagina. And, as all 
‘ {nails are hermaphrodites, the niale apparatus 
* for generation alfo proceeds from the left fide, 
* plate 7, fig. 1, b. This mark, which even the 
* moft practifed obfervers can with difficulty dif- 
* cover, becomes turgid at the feafon of their 
*‘amours. More than once I have had the good 
‘ fortune to furprife them in copulation, and‘ fee 
‘ their mode of proceeding, After they approach 
‘each other, it is entertaining to bekold how 
‘they mutually examine and re-examine with 
‘the head and neck, before uniting, and feem 
* as if by turns to excite each other and imvite to 
‘copulation. Then, having difpofed themfelves 
‘for amorous intercourfe, the male apparatus, 
§ turgid 
