INFUSORIAL ANIMALCULES. 29 



regularly disposed in a square or oblong form, the four central animalcules Fig. 12. 

 being usually larger than the rest. Their mode of increase is by self-divi- i 

 sion, and when this occurs, the group divides across the middle in two 

 directions, separating into four clusters, each containing four monads. No sooner 

 has a group thus separated, than each of the animalcules which composed it, 

 increases in size, and soon subdivides into four monads, and the original number 

 of sixteen is seen in every one of the four clusters. Ere long, these again sepa- 

 rate into four portions, and the species thus multiply interminably. The tablet, 

 though containing sometimes less than sixteen animalcules, never exceeds that 

 number. Its form is often irregular ; which is caused by the separation of 

 some of the monads from the cluster when they have attained their full growth. 

 Each of the individuals composing the group is connected with the rest by 

 means of six threads or tubes ; these, with the two cilia, a and 6, are seen in 

 figure 13, where a monad is exhibited attached to a portion of the 

 transparent case. The length of the tablet is not greater than one- 

 two hundred and eightieth of an inch, and that of each monad 

 ranges from about one-jive-hundredth to one-thousandth of an inch. 

 A single animalcule, when free from the shell, as delineated in figure 

 12, swims by the aid of its cilia in the direction of the length of its 

 body, with its mouth foremost, as other monads ; but the group 

 perform various evolutions, sometimes proceeding horizontally, 

 sometimes upwards, and again rolling on the edge like a wheel. The 

 extraordinary activity of these wonderful little beings is distinctly beheld, when a 

 small portion of coloring matter, as indigo, is introduced into the water in which 

 they are discovered ; then whirls and currents will be seen in the fluid, caused 

 by the vibration of the two cilia belonging to each animalcule. 



When a group is in progress, thirty-two of these organs are consequently in 

 motion ; twenty-four around the edges of the transparent case, and eight project- 

 ing from the central parts, and by their combined action, the cluster, enclosed in 

 its delicate envelope, proceeds as one body. And here we cannot but admire 

 the harmonious action of these curious groups. Each of the constituent indi- 

 viduals of a cluster is, of itself, a perfect being, gifted with peculiar powers, and 

 possessing a motion of its own ; yet, when united with fifteen others, all act in 

 concert, and move through their native element in new modes of progression. In 

 the case of the Siamese twins, the bodies of the two are bound together by a 

 strong muscular band ; and when they move in one direction it is because 

 their minds act in concert ; one cannot go north, when the other wishes to go 

 south ; in order to advance toward a given point, both must resolve to do so. In 

 this instance, the mutual consent can be readily expressed by words or signs ; 

 but who shall explain the nature of that connexion, by which sixteen distinct 

 animalcules are enabled to act with such unity of purpose, as to effect a common 

 end ; moving upward, forward, or revolving like a wheel, as their pleasure or 

 necessity demands ? Do they possess a common instinct which actuates every 

 member of the group at the same moment ; or is each monad possessed of its 



