Volvocina.] iNFrsoRiAL animalcules. 157 



happcnB when tlie larger animalcules have arrived at maturity, and 

 some of them have separated from the cluster. When they are all of 

 equal diameters, the group divides across the middle, hoth vertically 

 and horizontally, and separates into four clusters, each consisting of 

 foiu' animalcules. As soon as a cluster has separated, the respective 

 animalcules increase in size, and in a short time their surfaces appear 

 decussated, and they severally begin to form into regular clusters, 

 like the original one to which they belonged. They are of a beau- 

 tiful transparent green colour, and in swimming, the globules often 

 appear of an ellipsoidal figiLre (see fig. 40) ; their forms, when 

 viewed imder the microscope in the usual way, are so simple, and so 

 different from animated beings cognizable to unaided vision, that it 

 would be difficult to bring our reason to admit of their vitality, were 

 not their spontaneous motion clearly ascertained ; and when examined 

 under a high magnifying power, with proper illumination and 

 management, their structure rendered apparent. Figure 39 shows 

 a single free animalcule, with its two proboscides, and figure 42, a 

 highly magnified view of another, invested with the lorica. In this 

 figure is seen the disposition of the six cords or tubes which connect 

 it with the surrounding ones ; also numerous corpuscles within the 

 body. A combination of sixteen animalcviles (never more, but some- 

 times less) generally forms the square tablet or plate. 



In order to observe the structure of this highly curious and beau- 

 tiful creature, considerable adroitness is necessary in the management 

 of the microscope, while, a Little indigo, conveyed into the water with 

 the point of a camel's hair pencil, will be required to see the whorls 

 and currents set in motion around it. It is almost incredible what 

 power, comparatively speaking, these minute beings possess, notwith- 

 standing the speck they appear to occupy in the scale of creation. 

 The cuiTents are produced by the proboscides, two of which, as 

 stated above, are situated at the mouth of each individual, so that in 

 a tablet or plate, thii-ty-two, in aU — twenty-four placed at the edges, 

 and eight standing out fr'om the centre — are brought into action. 



The single animalcules (fig. 39) swim like the Monads, in the 

 dii'ection of the longitudinal axis of their bodies, with the mouth 

 foremost, but the plates have a variety of movements ; sometimes 



