188 HISTORY OF 



These animals have a progressive motion, which 

 is performed by that power they have of lengthen- 

 ing and contracting themselves at pleasure ; they 

 go from one part of the bottom to another ; they 

 mount along the margin of the water, and climb 

 up the side of aquatic plants. They often are 

 seen to come to the surface of the water, where 

 they suspend themselves by their lower end. As 

 they advance but very slowly, they employ a 

 great deal of time in every action, and bind them- 

 selves very strongly to whatever body they chance 

 to move upon as they proceed ; their adhesion is 

 voluntary, and is probably performed in the man- 

 ner of a cupping-glass applied to the body. 



All animals of this kind have a remarkable at- 

 tachment to turn towards the light, and this natu- 

 rally might induce an inquirer to look for their 

 eyes ; but however carefully this search has been 

 pursued, and however excellent the microscope 

 with which every part was examined, yet nothing 

 of the appearance of this organ was found over the 

 whole body ; and it is most probable that, like se- 

 veral other insects which hunt their prey by their 

 feeling, these creatures are unfurnished with ad- 

 vantages which would be totally useless for their 

 support. 



In the centre of the arms, as was said before, 

 the mouth is placed, which the animal can open 

 and shut at pleasure; and this serves at once as 

 a passage for food, and an opening for it after di- 

 gestion. The inward part of the animal's body 

 seems to be one great stomach, which is open at 

 both ends ; but the purposes which the opening 



