550 POLYGASTRIC ANIMALCULES ; VOLVOX. 



as their germs in a state of development. The Monads propa- 

 gate both by subdivision, and by the production of ova. The 

 former takes place either into two parts, by a transverse line of 

 separation ; or into four by a crossed division. 



1129. The next family to be noticed is that which contains 

 the Volwx and its allies. The nature of these beings was, until 

 recently, quite misunderstood. The Volvox globator, commonly 

 found in ponds, has a spherical form ; and its diameter is as much 

 as ^V of an inch, so that it is easily discovered by the unassisted 

 vision. This sphere, when examined with a high magnifying 

 power, is seen to consist of a thin transparent pellicle, studded at 

 regular intervals with minute green spots. Further examina- 

 tion makes it evident, that each of these spots is an individual 

 animalcule of the nature of a Monad. From every one of these, 

 two filaments proceed, which pass through the general envelope, 

 and vibrate in the surrounding fluid ; so that, the whole surface 

 of the sphere being beset by them, it is made to perform very 

 active movements. It is usually seen rolling over and over like 

 a ball ; sometimes spinning in the same place, like a top ; or 

 gliding along smoothly, without turning itself. Sometimes its 

 motions are slow ; at others rapid. The general envelope is 

 traversed by canals, which seem to connect the different indivi- 

 duals together ; in the same manner as the Polypes of a Sertu- 

 laria ( 1056) are united by their common circulation. Within 

 the parent sphere may generally be seen other globes of darker 

 colour, and varying in number from one or two to twenty. 

 These are young formations of a similarly-compound nature. 

 They appear to have taken their origin from the subdivision of 

 one of the Monad-like beings, which enter into the composition 

 of its parent ; and for some time they remain attached to its 

 inner wall. They afterwards detach themselves, however, and 

 may be observed revolving in its cavity, by the action of their 

 own ciliary filaments. After a time the parent globe bursts, 

 and the young ones swim forth, and speedily undergo the same 

 changes. Their dark colour appears due to the closer approxi- 

 mation of these component Monads ; the transparent polypidom^ 

 for so it may almost be termed, being developed between them at 



