DIPS INTO MY AQUARIUM. 87 



affinities. The earlier arrangement of Huxley, in which they are 

 regarded as a group of Scolecida or lower worms, such as inhabit 

 water or are parasitic on other animals, is adopted by Nicholson, 

 and is undoubtedly the safest one to follow at present. 



But in whatever way the matter may be settled, these pretty 

 creatures must certainly be exalted to a much higher position than 

 they occupied when grouped with many other and very different 

 organisms in that confused jumble of the earlier geologists which 

 they called Infusoria. We have here another wonderful illustra- 

 tion of the rapid advance of modern biological science and a 

 splendid testimony to the value of the microscope as a handmaid 

 to scientific research. 



Mr. Gosse prefers to call the gizzard by the name of mastax^ 

 and contends that it is really a mouth. He says it consists of 

 muscular fibre. Out of it a funnel leads upwards, while a sort of 

 oesophagus runs downwards to the stomach. Inside the mastax 

 are two organs, which work like hammers and supply the place of 

 teeth. They pound down the particles of food on an anvil and 

 prepare them for digestion. All this is curious to behold, but to 

 see these processes we need higher powers and more elaborate 

 arrangements. Those, however, who are skilled in the use of the 

 compressorium and can examine the rotifer with a good ^-inch 

 lens will be amply repaid for their trouble. 



The respiration of Rotifers is said to be carried on by means of 

 what is termed a " water vascular system," consisting of two tubes 

 filled with a watery fluid, from which many shorter tubes proceed 

 into the internal parts of the body. The two large tubes run into 

 a " contractile bladder," which pulsates like a heart, and so keeps 

 up the circulation. 



One curious fact about the Rotifers must not be omitted, and 

 that is, the females are much more highly organised than the 

 males. The males, however, are more free than the females, and 

 so probably both are content. 



While watching the Rotifer for any prolonged period of time, 

 we are sure to see it, sooner or later, loosen its hold of the twig to 

 which it was anchored, when it will swim away with cilia in action, 

 or perhaps will tuck in its wheels and crawl in and out amongst 

 the tangled weeds. We can now see that the tail or foot by which 



