FEESHWATER LIFE. 95 



forth in the act of feeding. The cilia will be seen to move in such rapid 

 and well-timed succession as to look like revolving wheels ; and so perfect 

 is the optical illusion that you feel how appropriately these creatures 

 have been named " Wheel-bearers," or Eottfera. 



Their exact place in the animal series has not yet been finally 

 determined. Provisionally they may be referred, as an order, to the 

 somewhat miscellaneous class Scolecida, in the sub-kingdom Annuloida. 

 On the whole, they appear to have strong affinities to the worm-like 

 animals of the class just mentioned, as well as certain points of 

 resemblance to the lower crustaceans, and to the larval forms of 

 Echinodermata. 



The Eotifera attain a maximum size of about l-36th of an inch. 

 Some are as small as l-400th of an inch, or smaller. They are of a 

 higher type of organization than the Infusoria, with which they were 

 formerly grouped, since they have an obscure segmentation of the body, 

 a completely separate alimentary canal, and a water- vascular system ; 

 and they never multiply by .budding or self-division. They have a right 

 and left, a dorsal and ventral, and a head and tail aspect; the end 

 answering to the head moving habitually forwards, with the back upwards. 

 Some are fixed by a foot-stalk to water-plants dui'ing the whole or the 

 greater portion of their existence ; but the majority are free-swimming. 

 The former use the ciliated wreath to urge food to theu* mouth ; the 

 latter use it as a locomotive organ when in motion, and a feeding organ 

 when at rest. Few things are more strikingly beautiful than this ciliated 

 wreath in full activity. At intervals it is drawn in and tucked out of 

 sight, so as completely to alter the look of the animal. Biit after a time 

 it issues forth again, expands, and resumes its work. The food, received 

 by a distinct mouth, is caught by a sort of champing gizzard, which has 

 been likened to a pair of toothed hammers and a double anvil, and is 

 there crushed small before admission to the stomach. In this I'eceptacle, 

 which is of variable size, the food is digested. The refuse of digestion 

 then passes along an intestine ; and finally, in most kinds, though not in 

 all, is got rid of by a distinct orifice, connected with a cloaca, into which 

 the ovary and a contractile vesicle also open. There is no heart ; but a 

 water-vascular system is present, consisting of two convoluted tubes, 

 one on each side, furnished at intervals with short pipes hned with cilia, 

 which lead into the general cavity of the body. The lower ends of these 

 tubes open into the aforesaid contractUe vesicle ; and thus, the pulsations 

 of the vesicle and the vibrations of the cilia keeping up a current, the 

 fluids of the body are refreshed by being brought into communication 

 with the outer water. 



Of the nervous system, the following are the main features : — Near 

 the back of the neck there is found a ganglionic mass, on which are 

 mostly seated one or more eye-spots, generally of a bright crimson colour. 

 Projecting from about the same place may often be seen a little tele- 

 scopic feeler, armed at the tip vdth minute bristles ; or the bristles may 

 be sessile in a small hollow. Muscles pass lengthwise from end to end 

 of the body, and ring-wise at intervals round it, by which the external 



