10 AN ANIMATED CRICKET-BALL. 



which the investing gelatinous mass is of a globular form, and 

 encloses about thirty Monads of a dark-green colour, which have 

 a peculiarly elegant appearance in the centre of the transparent 

 sphere." 



It is a terrible coming down from the romantic views of 

 Ehrenberg, no doubt, to assign these various bodies, simple and 

 compound alike, to the vegetable kingdom, but such is un- 

 questionably their true position 5 for they are now ascertained, 

 beyond all reasonable doubt, to be nothing more than the suc- 

 cessive stages of a humble plant the Protococcus pluviulis; 

 the so-called simple monads being merely the early " motile " or 

 active germs of the plant, and the compound or associated forms 

 the subsequent phases which the plant assumes by the continued 

 self-division of its original cells. 



But a far more extraordinary example of these composite 

 vegetable structures, formerly ranked with the Monads, is the 

 famous Volvox glolator, which has not unnaturally excited more 

 astonishment than any other member of this most strange 

 association of organisms. The Volvox is by no means uncommon 

 in our ponds and ditches, and as it attains a diameter of one- 

 thirtieth of an inch, it may easily be detected by the naked eye 

 when the drop of water containing it is held to the light. Seen 

 in this manner, the Volvox appears a minute green globule gently 

 moving about in the water ; but when viewed with a moderate 

 magnifying power, the globule is seen to be a hollow pellucid 

 sphere, studded at regular intervals with minute green spots, from 

 each of which proceed two long cilia, by the united action of 

 which the little globe moves through the water. Ordinarily it 

 moves onward with a rolling kind of motion, a sort of self-bowling 

 cricket-ball ; but occasionally it glides along without turning on 

 its axis, and more rarely still, it may be seen twisting round 

 like a top without changing its position. In the interior of the 

 Volvox a number of smaller globes may generally be seen, some 

 adhering to the inner surface of the investing sphere, and others, 

 more advanced, lying freely within the cavity, revolving like 

 satellites, not around, but within the parent sphere. If the ob- 

 servation be continued for a short time, the larger globe will be 

 seen to burst, when the imprisoned globules float freely away to 

 begin an independent existence. 



Long after the Volvos was quite familiar to microscopical 



