Mick o s cx> p i cal Essays* 



447 



^eft like a broad point, but which can be moved to and from 

 each other very brifldy with a vibratory motion, fee Fig. 33. 



The form and lituation of the two branches is fometimes 

 changed, the ends thereof becoming more round, and the vibra- 

 tory motion is altered to a rotatory one : this alteration is repre- 

 fented at Fig. 34 : the head alfo appears in this figure. The 

 thorax is annexed to the lower part of the head, it is mufcular ; 

 within it there is a moving inteitine, which has been fuppofed to 

 be either the lungs or the heart of the little creature, fee b, Fig, 



A communication is formed between the thorax and the ab- 

 domen by means of a fhort veffel c, whofe alternate contractions 

 and dilatations occafion the abdomen to rife and fall alternately,, 

 having at the fame time a fort of periftaltic motion. The food 

 is conveyed through this veffel into the abdomen, where it is 

 digefted; it is then, difcharged by the anus* which is placed near 

 the taili 



The tail has three joints, and is cleft or divided at the extre- 

 mity, by which means it can better fallen itfelf to fuitable objects. 

 It is in generar projected from the lower end of the (hell, moving, 

 nimbly to and fro, ferving the animal as a rudder when it is 

 Iwimming to direct it's courfe.. 



When the water in which the little animal is placed is nearly 

 dried away, or when it [has a mind to compofe itfelf to reft, it 

 contraas the head and fore-part of the body, and brings them 

 down into the {hell, and pulls the tail upwards, fo that the whole 



