l^^ PLxV^'ARIA ARETHUSA* 



numbers of the scorpion, and the deleterr- 

 ous activity of its poison, decrease as it re- 

 moves from under the hne ; and the necta- 

 rious collections of the bee are adapted to 

 those regions only which admit the bloom 

 of flowers. Let us traverse the shores of 

 our native islands ; within a determinate 

 boundary, we shall fmd a particular tribe 

 numerously disseminated, and in vigorous 

 life ; proceeding a little onwards, fewer ap- 

 pear in their. haunts; and advancing still 

 farther, the race totally vanishes.— Then 

 another is seen, which, from at first being 

 scantily associated, becomes at length the 

 sole tenant of the territory. 



Division II. Planaria Graminea, Fig. 16. 

 --It must not be conceived, that all the 

 animals hitherto ranked under the genus 

 planaria by naturalists, bear a common re- 

 semblance, either in organization or pro- 

 pensities. So wide a difference in both ap- 

 pears among them, that one intermediate 

 tribe, somewhat more approximate to the 



