286 ZOOLOGY 



increase by transverse cli\'ision; l)ut periodically they roll up 

 into a sphere, form a tough shell, and divide into numerous 

 " spores," which, under favorable conditions, are set free 

 in great numbers. 



The third class, known as lash-animalcules, or Flagellata, 

 is well represented by a common form, Euglena (Fig. 271). It 

 is of microscopic size, but occurs in such numbers as often to 

 give a decided green color to the pools of water it inhabits. It 



• --■- "^ '*' spindle-shaped, and bears a lash at 



' j^^^^-'^j^^^'^H^ its anterior end. At the base of the 



' j^iv•vf!^:?'•••'•'•vv<')^'•''^^^^^ ' ^'^^^^ i^ ^ ''^^^■^ " ej'espot." 



fr^V!(i|"'Vv:|i ^ ;.■■'-;•;.•.".';■'-' 't ' Allied to Euglena is Volvox,^ a 



V;." v;'- ' '■'■•'^ " ,' spherical, multicellular organism, half 



, ^Jj" ' ■ .- : animal and half plant, and forming a 



i ^^■^*i«Jl^"^ J ^^-'^'t °^ connecting link between the 



" Protozoa (or one-celled animals) and 



Fig. 272. — Yoltox globator. , . ,, , , • , 



Much magnifieci. Photo, the multicellular higher organisms, 

 of the living animal. Volvox occurs abundantly in our 



ponds, and gets its name from its manner of revohang in the 

 water (Fig. 272). 



To the fourth or highest class of Protozoa has been restricted 

 the name Infusoria formerly applied to all Protozoa. In the 

 Infusoria the body has a definite and more or less permanent 

 form. The hair-like appendages (cilia), b}' which they move 

 about or seize their prey, cannot be retracted. 



Of all the Infusoria, none is more abundant than Para- 

 moecium. It occurs ever\'-where, principally in stagnant fresh 

 water, but also in salt water. It lives entirely on vegetable 

 food, and is sure to abound wherever plant matter is under- 

 going decaj^ When a culture is once started from a hay in- 



' From solvere, to roll. 



