Characteristics of Rotifers. 283 



running down the gullet. Three kinds of eggs have been dis- 

 tinguished — common eggs, intended for immediate hatching ; 

 winter or resting eggs, designed for preservation probably till 

 the next season, like the statoblasts of Flumatella and other 

 Polyzoa; and male eggs. The winter or resting eggs are 

 usually rough and large. 



The known males are shortlived, and not provided with any 

 digestive machinery. They seem to be simply locomotive 

 organs of fecundation, whose services are occasionally required, 

 the ordinary process of reproduction being carried on by the 

 females alone, as is the case with those pests of the greenhouse 

 and garden — the Aphides, or plant-lice. Such a method of 

 propagation has more or less analogy to the multiplication of 

 plants by buds or cuttings, instead of by germs fertilized by 

 pollen and giving rise to true seeds. 



The existence of eyes in rotifers has already been men- 

 tioned. They often exhibit the brilliance and tint of the ruby, 

 and the single large eye of the BracMons may be specially 

 noticed for its conspicuous beauty. In many rotifers the eyes 

 vanish as the individual grows old, and it is often difficult to 

 detect them. Dark ground illumination is frequently very 

 useful for this purpose. The eye is probably of limited use, 

 and may not form true pictures in the highest sorts of rotifers, 

 though a refracting body or crystalline lens is said to be always 

 present. There are many gradations in nature from eyes that 

 seem only capable of making known the presence of light to 

 those which form elaborate pictures on the retina, and by 

 means of appropriate nerves supply definite information to the 

 brain. Probably, the rotifer eye occupies one of the lower, 

 though not the lowest position in the scale. 



The calcar or spur of the common rotifer, often seen pro- 

 jecting like a pigtail, and similar organs on other species are 

 probably feelers. They are tubular structures, fitted with a sort 

 of moveable piston, terminating in a tuft of cilia. A sense 

 of touch is probably diffused over the soft parts of the 

 body, and the tentacles may be very sensitive to vibrations 

 affecting the fluid in which the animal lives. It is also proba- 

 ble that the sense of taste exists in a rudimentary form, as it 

 is very common to find rotifers rejecting particles which so far 

 as size and consistency goes might be swallowed for food. 



No perfectly satisfactory classification of rotifers has yet 

 been proposed. Ehrenberg divided them into groups, founded 

 upon his conception of the form of the rotary organs, but a 

 modification or rather expansion of Dujardin's classification 

 will be found more convenient for general use, and may stand 

 as a provisional arrangement, pending a more thorough exami- 

 nation of the whole series. Dujardin calls rotifers Systolides, 



