160 MICROSCOPY FOR BEGINNERS. 



mouth at the wounded end, and shoots forth arms more 

 or less speedily as the heat is favorable. If the polype 

 be cut the long way through the head, stomach, and 

 body, each part is half a pipe, with half a head, half a 

 mouth, and some of the arms at one of its ends. The 

 edges of these half pipes gradually round themselves 

 and unite, beginning at the tail end ; the half mouth 

 and half stomach of each becomes complete. A polype 

 has been cut lengthwise at seven in the morning, and in 

 eight hours afterwards each part has devoured a worm 

 as long as itself." He also sliced them across, and found 

 that each piece developed a cluster of tentacles, and he 

 finally turned them inside out, and in a few days the 

 maltreated creature swallowed food, although its old skin 

 was now lining its stomach, and its old stomach mem- 

 brane had now become its skin. 



There is a peculiar parasitic Infusorium (Fig. 1305) 

 often seen in considerable numbers gliding rapidly over 

 the body and arms of the Hydra, especially of II. vi- 

 ridis. They do not seem to be objectionable 

 guests, as the Hydra never appears to notice 

 them. It is said that they infest sick or 

 weakly victims only, but that is not according 

 to the writer's experience, if the condition of 

 the Hydra may be judged by appearance, ac- 

 tivity, and appetite. One of these parasites 

 is shown in side view (Fig. 130&). It is shaped like 

 a short dice-box, with a circle of fine cilia at each 

 end, but none on the rest of the body. It glides along 



