14 THOUGHTS ON ANIMALCULES. 



them to a fixed point, and then drawing its body to the 

 same spot; the various attitudes it assumes in these 

 movements are shewn in the figures : a denotes the base, 

 or pedicle; and b, the head, or mouth. 



The locomotive actions of the hydra are slow, but 

 may readily be observed if that part of the glass to 

 which the animal is attached be turned from the win- 

 dow ; for the polypes, though destitute of any visual 

 organs, always move towards the light, and quickly 

 begin to shift from the dark side of the vessel, standing 

 at first erect upon the pedicle, and throwing their arms 

 forwards and fixing them, thus bending the body arch- 

 wise, and at length drawing the tail towards the head, 

 as shewn in pi. i, fig. 9. 



II. The COMMON POLYPE, (Hydra vulgaris, pi. i, 

 figs. 2, 4, 8). The body is of a cylindrical form, and 

 of an orange-brown colour. It has from seven to twelve 

 arms, which are a little longer than the body. 



Fig. 2, a polype contracted. 



Fig. 5, a front view of an individual still more col- 

 lapsed. 



Fig. 4, a polype, with two young ones, of different 

 ages, shooting out from the body. 



III. The LONG-ARMED POLYPE, (Hydra fusca, pi. i, 



