222 



Microscopical Essays. 



extremity ; by this means a hollow fpace is formed, and the 

 bladder of air pent up in it looks like a pearl, Fig. 2, Plate XI. 

 It is by the afftftance of this bubble, or little balloon, that the in- 

 fect raifes itfelf again to the furface of the water. If this bubble 

 efcapes, it can replace it from the pulmonary tubes ; fometimes 

 large quantities of air may be feen to arife in bubbles from the 

 tail of the worm to the furface of the water, and there mix with 

 the incumbent atmofphere. This operation may be eafily feen 

 by placing the worm in a glafs full of water, where it will afford 

 a very entertaining fpeclacle. 



The fnout is divided into three parts, of which that in the 

 middle is immoveable ; the two other parts grow from the fides 

 of the former ; thefe are moveable, vibrating in a very lingular 

 manner, like the tongues of lizards and ferpents. The greater! 

 ftrength of the creature is fixed in thefe lateral parts of the fnout ; 

 it is on thefe that it walks when it is out of the water, appearing 

 as it were to walk on it's mouth, ufing it, as the parrot does it's 

 beak, to move (climb) with greater advantage. 



We fhall now confider the external figure of this worm, as it 

 appears with the microfcope. It is fmall towards the head, larger 

 about thofe parts which may be confidered as the thorax, it then 

 grows fmaller, converging, at the abdomen, terminating in a 

 fharp tail, furrounded with hairs in the form of the rays of a 

 ftar. 



This worm, the head and tail included, has twelve annular 

 divifions, 2,2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, Fig. 3, Plate XL 

 It's ikin refembles the covering of thofe animals that are provided 



with 



