THE SYNCH^ETA BALTICA. 



'i6& 



their ordinary position when keeping their wheels in action for 

 a supply of food or of water ; but they have no difficulty in 

 letting go their hold, and either creeping along by alternate 

 contractions and extensions or swimming away in search of a 

 new attachment. From the neck projects a telescopic spur. 

 supposed to be an organ of respira- 

 tion, and just below this are seen two 

 minute red specks, supposed to be 

 eyes. The first rotifer was discovered 

 by Leeuwenhoek, in 1702 ; now more 

 than 180 species are known, and new 

 discoveries are constantly adding to 

 their numbers. They are chiefly found 

 in sweet water, but some are inhabitants 

 of the sea, as, for instance, the Syn- 

 chceta baltica, remarkable for its lu- 

 minous powers. It measures about T -J-g- 

 of an inch in length, and but 3^-5 in 

 width, so that it is invisible to the 

 sharpest unassisted sight : but when 

 viewed through a microscope, it appears 



as a beautiful and richly organised 



creature, clear as glass and perfectly 



colourless, except that its stomach is 



usually distended with yellow food, 



and that it carries a large red eye, which 



glitters like a ruby. 



" Its motions too," says Mr. Grosse, 



"are all vivacious and elegant. It 



shoots rapidly along or circles about 



in giddy dance, in company with its 



fellows, sometimes near the surface, at 



others just over the bottom of the vase 



in which it is kept. Occasionally the 



foot with the tiny toes is drawn up 



into the body and then suddenly thrown 



down, and bent up from side to side as a dog wags his tail. 



Sometimes the rotatory organs are brought forward and then 



spasmodically spring back to their ordinary position, when the 



little creature shoots forward with redoubled energy. In all its 



actions it displays vigour o^d. precision, intelligence and will." 



PhUodirja roseola. — (Highly 

 magnified.) 



a. Respiratory tube. 



b. Alimentary canal. 



c. Cellular mass. 



d. Terminal intestinal pouch. 



e. Anal orifice. 



