INFUSORIA ROTATORIA. HYDATINE. 



91 



organs of the senses, except perhaps their tentacles, which may 

 serve them for the sense of touch. 



3. Most Zoophytes are also destitute of blood-vessels, and they 

 have no special organs of respiration, this function being per- 

 formed by the whole surface of the body. Some of them have 

 a mouth armed with teeth, a digestive canal and anus ; but in 

 others, the digestive cavity has a single opening, which serves at 

 the same time both for mouth and anus. 



' 4. This Branch of the animal kingdom is divided into six 

 classes ; namely, Infuso'ria rotato'ria, JEntozo'a, Infuso'ria poly- 

 gas' trica, Echinoder 'mata, Acale'pha, and Polypi. 



CLASS OF INFUSO'RIA. ROTATO'RIA. 



5. These creatures are so extremely small, that prior to the 

 discovery of the microscope, tlieir existence was not even sus 

 pected, and yet their structure appears to be as complicated as 

 any other animal of the same branch. 



Although the instruments by means of 

 which they were observed, caused them 

 to appear to -be two or three hundred 

 times larger than they really are, no 

 distinct organ was discovered in them, 

 and for a long time they were regarded 

 as creatures composed of a kind of 

 animated jelly only, which lived by im- 

 bibition. But the researches of some 

 modern naturalists, especially Professor 

 Ehrenburg, of Berlin, have shown how 

 much we were mistaken in regard to 

 these animalcules; and we are aston- 

 ished, not by the simplicity of their 

 structure, but by their complicated 

 microscopic organization. 



6. These animalcules are found in 

 stagnant waters, and also in water in 

 which animal substances have been 

 soaked. Their body is partially trans- 



Explanalion of Fig. 81. Anatomy of a Hydatine, a microscopic animal- 

 cule, resembling a rotifer : a, the vibratory cilia ; 6, a fleshy mass which 

 surrounds the mouth and sets the jaws in motion ; c, the stomach ; rf, 

 cloaca ; e, anus ; /, salivary glands ; g, ovaries ; A, vessels. 



3. How do Zoophytes breathe ? 



4. How is the Branch of Zoophytes divided ? 



5. What are the characters of the rotatory Infuso'riae ? 



6. Where are these animalcules found? 



Fig. 81. HYDATINE. 



