86 DIPS INTO MY AQUARIUM. 



position at once. A spectacle is now presented to us which, if 

 one has never seen it before, is sure to awaken admiration and 

 to call forth expressions of delight. Here are the wheels 

 apparently turning round with astonishing rapidity. Just under 

 them is a gizzard actively at work. These wheels are not really 

 rotating, but they are made up of a circle of fine hairs called cilia^ 

 which lash the water in quick succession, and that begets the illusion 

 of revolution. By the incessant play of these cilia, the water in 

 their vicinity is kept in a state of agitation, and as a consequence 

 multitudes of minute objects are brought within reach of the 

 creature's mouth. Some of them are evidently rejected by the tiny 

 epicure, for they fly away just as they seemed on the point of 

 being swallowed, while others, more acceptable, are seen to go 

 swiftly into the hungry maw of the animal. 



A further inspection will show that the Rotifer is much more 

 highly organised than we might at first sight have supposed would 

 be the case with so minute an animal living under such conditions. 

 Separate and specialised organs are soon observed. The head is 

 quite distinguishable from the general mass of the body ; the 

 outer portion, which we will call the skin if you like, is clearly 

 different from the internal portions ; there are two small, bright 

 spots, which are probably organs of vision ; while we can also 

 clearly perceive a small gangHon of nerve substance which fulfils 

 the office of brain. There are also other organs inside the body^ 

 all of which have important functions to perform, especially in the 

 reproductive processes. 



The first question that a real student of these minute creatures 

 will ask is as to their proper place in the zoological scale, and this 

 is a point about which perfect agreement has not yet been arrived 

 at amongst zoologists. Professor Huxley ranks them very near to 

 the lower worms, and considers them to be " the permanent forms 

 of echinoderm larvae " — that is to say, they agree in many points 

 with an imperfect sea-urchin or star-fish. Mr. Gosse, who has 

 studied these creatures more industriously than any other micro- 

 scopist, and was universally admitted to be facile princeps in this 

 realm of zoology, places them still higher in the animal kingdom ; 

 and while admitting their connection with the worms, seems 

 inclined to associate them with insects in regard to their structural 



