PROTOZOA 



191 



give rise to a great number of smaller organisms. In 

 the malaria parasite, which is conveyed to man by the 



Drawing by R. Weber (after Leidy) 



FIG. 40. Shells of three species of Difflugia. A, D. capreolata. B, D. corona. 

 C, D. acuminata, variety inflata. Although Difflugia corona presents marked 

 variations, it never assifmes the form of D. acuminata or D. capreolata. Distinctive 

 characters are not confined to the shell; one species (D. rubescens) has the contained 

 animal of a beautiful brick-red color. Greatly magnified. 



mosquito, sexual reproduction occurs in the body of the 

 insect, but asexual sporulation takes place in the human 

 blood. 



Gregarines are sporozoans usually found in the ali- 

 mentary canal of insects and other arthropods. One 

 common species lives in the earthworm. 



6. The Rhizopoda include many of the most common The Amiba 

 fresh-water Protozoa, which possess neither flagella nor 

 cilia, but move slowly about by means of projections of 

 the body, called pseudopodia (singular, pseudopodium) 

 or false feet. The Amiba (or Amceb.a) is a naked form 

 common in ponds. 1 When at rest it is spherical, but its 

 protoplasm flows outward to form elongated pseudo- 

 podia. Within the body can be seen nucleus and con- 



1 This animal was originally called Proteus, on account of its changing 

 form, but it was found that the name had previously been used for another 

 animal. Amiba was then substituted, with the spelling here given, though 

 it is more usual to write Amoeba. 



