The Microscope. 233 



9 and 21. Every part seems capable of great extension and con- 

 traction: to examine the wonderful mechanism of its parts will 

 afford hours of amusement; it being transparent, the motion of the 

 heart and other internal parts may be seen: it appears continually 

 to be hunting after its prey, has a large mouth, and is furnished by 

 nature with an amazing piece of machinery or wheel-work to pro- 

 cure its food; the wheel- work projects from the head, and turns 

 round with great velocity, causing a rapid current of water to be 

 brought from a considerable distance to its mouth, and by this 

 means supplying it with food; as these wheels are transparent, it 

 is very difficult to determine by what contrivance they move, or 

 what their real figure is. Though they seem exactly to resemble 

 wheels moving round upon an axis, as the insect is capable of 

 thrusting these parts out or drawing them in at pleasure, their fig- 

 ure is completely altered by so doing, and they appear in the vari- 

 ous forms represented in figs. 8, 9, 10. 



Sometimes they turn themselves into round globules or balls, 

 when done feeding: they then draw in their wheels, and their tails 

 remain fastened to the slip of glass they were placed on, as in fig. 

 7. All their actions seem to imply sagacity and quickness of sen- 

 sation, for at the least touch or motion in the water, they draw in 

 their wheels: though small creatures, they may be compared to 

 whales in proportion to some of the animalcules in the same drop 

 of water; these are their prey, which they draw towards them by 

 the current of water which their wheels excite, fig. 9. None of 

 them can cross this current without being drawn into its mouth. 

 Some of them have eggs or spawn attached: and by procuring a 

 number of them, and watching them attentively, the young one 

 may be seen to burst the egg, and gradually force its way out, fig. 

 12, in doing which, it is greatly assisted by the tail of the parent, 

 for by moving it to and fro, and striking the shell, it breaks the 

 egg, and the young one, by the assistance of its wheels, is thus 

 enabled to force its way. 



A small species of the wheel insect is found in the infusion of 

 hay, after sometime standing, as in fig. 5. This animalcule pos- 

 sesses the wonderful property of retaining life for years when out 

 of the water; in this state, life may be said to be latent, but, short- 

 ly after the insect is placed in water, it resumes its functions and 

 becomes as active and vigorous as before. 



The Satyr, or small Water Spider In ponds, and 



in several infusions, a little crustaceous insect is to be found, fig. 



13. The shell is so exceedingly transparent, that it can hardly 



be discerned — it covers the whole of its back. Four legs or fins 



30 



