286 GENERAL ZOOLOGY 



(Fig. 142, 6), which penetrates to the outer wall of the stomach 

 of the mosquito, where it increases in size to form a large 

 sphere (Fig. 142, 12). In a short time the sphere subdivides 

 into countless extremely minute blasts (Fig. 142, 17, l). These 

 make their way through the body-cavity of the mosquito to 

 the salivary glands. Penetrating to the interior of those 

 glands, the blasts enter the ducts, and are carried outward 

 and down the insect's proboscis by the saliva when the 

 mosquito bites another person. Then in the human blood 

 the blasts enter the red corpuscles and become amcebulce, 

 thus completing a cycle. 



Prominent among the scientific men who since 1896 have 

 discovered the facts of the life-history of the malarial para- 

 site are Dr. Ross, of India, and Professor Grassi, of Italy. 

 Upon their discoveries, and those of others, are based the 

 numerous operations against the mosquito in the vicinity of 

 large cities. 



Paramoecium. Perhaps no member of the phylum under 

 discussion in this chapter has been observed by more 

 students than has the slipper-animalcule, Paramce'cium cau- 

 da'tum (Fig. 143 A, B) ; and no member of its phylum has 

 been so frequently made the basis of scientific discussions of 

 cell-structure and cell-physiology. Paramoecium lives in stag- 

 nant pools of fresh water in all lands. Specimens may be 

 obtained in countless numbers by placing a quantity of hay 

 in a jar of ordinary water and leaving it to stand for a few 

 weeks. The bacteria developed in the decaying hay furnish 

 an inexhaustible food-supply for the animals. 



As in Amoeba, Euglena, and Plasmodium, the entire body 

 of Paramoecium is a single cell. The cell when moving 

 freely has a definite shape, although it changes constantly in 

 outline, owing to the fact that the irregularities in the body 

 are whirled into view as the animal swims along in a slender 

 spiral path. 



