CHAPTEK VIII. 



Older III. PLOiMA. 



Sivimming with their ciliary wreath, and (in some cases) creeping with their toes. 



It has been already seen ' that our typical Kotiferon was drawn from the ranks of 

 the PLOIMA; and rightly so, for the number of its genera, the abundance of its species, 

 the restless energy, perfection of structure, and superior intelligence of its members, 

 clearly entitle the third order to be considered the typical one. It is true that Peclalion 

 makes a still nearer approach to the Arthropoda in its structure than does any species 

 of the PLOIMA, and must be ranked above them in the scale of the animal kingdom ; but 

 it is almost (if not quite) the only representative of its order, and therefore unfitted to 

 be taken as a tj'pe of the class. 



In the Free-Swimmers the mastax reaches its highest development, and is often used 

 like the mandibles of an insect. Mr. Gosse and I, as weU as other observers, have seen 

 these active creatures seize their prey with their jaws, and watched them nibbling the floc- 

 cose sediment on the stems of water-plants, or slitting up the cells of algse and the skins of 

 infusoria in order to extract their contents. Indeed, the snapping of the protruded jaws 

 among some of the Notommatadca is so vigorous that it is difficult to see it and not to 

 fancy that we hear the snap ; and on one occasion, even, the fierce atom has been seen 

 to give itself a fatal lock-jaw by its outrageous snatch. 



Li this order, too, as might have been expected from their habits, the nervous system 

 is conspicuous, the ganglion being large, and the nervous threads from it to the various 

 organs of sense more easily traced than in the first and second orders. The eyes, too, 

 have often obvious lenses, and the tactile organs are numerous and well-developed. The 

 vascular system, whose probable respiratory functions must be of the utmost importance 

 to these restless animals, is unusually well developed. It spreads a network of coiling 

 tubes close under the cuticle, and not unfrequently ends in a contractile vesicle so large 

 as to fill, when distended, an important portion of the body-cavity. 



In fact, the whole structure of the order shows its members to be well equipped for 

 the energetic life which observation proves them to pursue. They haunt the alga; on 

 pond walls, coast along the water-line among decayed leaves and floating dibris, divs 

 down to the bottom to explore the muddy sediment, or boldly put ofl:' from shore, and 

 sail out even into the middle of such a lake as that of Zurich. No doubt the marvellous 

 coroiiffi of the Ehizota and BdcUoida will always continue to attract the expert and 

 amateur alike ; but to obtain an adequate notion of the structure of the Eotifera, and of 

 what may fairly be termed their mental capacities, the inquirer must turn to the study 

 of the PLOIMA. 



Sub-Order Il-lokicata. 



Integument flexible, not stiffened to an inclosing shell ; foot, when inesent, almost 

 invariahli/ furcate, but not transvcrsclij wrinkled; rarel'j more than feebly telescopic, 

 and partially relraclilc. 



< r. 1. 



