250 MICROSCOPY FOR BEGINNERS. 



short distance with a jerk, only to allow itself to float 

 back to the starting-point. A glass jar well stocked 

 with these pretty creatures leaping up and down ir- 

 regularly and incessantly is an interesting sight. Un- 

 der the one-inch objective the little animal is more than 

 interesting. 



5. CYPRIS (Fig. 161). 



The shell entirely surrounds the animal, so that the 

 little creature, when danger threatens, shuts itself in as 

 completely as a clam or a mussel, and allows itself to fall 

 to the bottom. The form varies from an oval to a kid- 

 ney shape, according to the species, and the color may 

 be green or brown, or whitish and 

 marked with several dusky bands. It 

 may be smooth, or entirely covered 



r 



. IClCypris 



ders may be fringed. The shell is 

 never opened wide, but the legs and feathery antennae 

 project from a narrow cleft between the valves, the lit- 

 tle animal swimming rapidly by their aid, or creeping 

 about the slide or over the aquatic vegetation. Cypris 

 is reproduced by eggs, but " the mass of eggs, including 

 about twenty-four, is attached by the female to water- 

 plants with the aid of a glutinous secretion, an opera- 

 tion which lasts about twelve hours." 



6. CAMPTOCERCTJS (Fig. 162). 



The shell is elongated, somewhat quadrangular, trans- 

 parent, and marked by lines traversing the surface 



