The Protozoa 



139 



Muttkowski examined over 6,000 fish stomachs and found only one 

 mosquito wriggler. Another observer examined about 2,000 specimens 

 of gambusia, the so-called "mosquito-destroying top minnow," and found 

 mosquito wrigglers in only about two per cent of the fish. 



PARAMOECIUM 



The animal now to be studied is the Paramoecium (Fig. 52), a 

 member of the class Infusoria. 1 Paramoecia are often called slipper 



animalculae because they are shaped 

 like a slipper, or more correctly like 

 a cigar. The distinctive characteristic 

 of this animal is that its entire body 

 is covered with little hair-like projec- 

 tions, called cilia. The rapid move- 

 ment back and forth of these cilia 

 (especially those of the oral groove 

 which beat faster than those on other 

 parts of the body), causes the animal 

 to be propelled through water. An 

 oral groove extends obliquely back- 

 ward from the forward end and 

 empties just a little behind the middle 

 Sfff?*^ portion of the body. The mouth is 

 situated at the end of the oral groove, 

 so that as the animal swims and con- 

 stantly revolves, various substances 

 are forced down this groove, and, as 

 they reach the end of the groove, are 

 thrust into the mouth proper. It also 

 has an endosarc and ectosarc like in 

 Amoeba, and an additional membrane 

 or pellicle, sometimes called the 

 cuticle. This is demonstrated by placing a drop or two of 35 per cent 

 alcohol in a drop of water where some of the Paramoecia are found. The 

 pellicle will raise like a blister, showing that this part is separate and 

 distinct from the rest of the animal. Immediately beneath the cuticle 

 is a layer of spindle-shaped cavities in the ectoplasm. These cavities are 

 filled with a semifluid substance. They are known as trichocysts 

 ( ), supposed to be weapons of offense and defense 



(Fig. 53). If a little acetic acid, or ordinary blue or green fountain-pen 

 ink, is added to the water, these trichocysts explode, and the long threads 

 which they contain are discharged. 



There are two contractile vacuoles, one close to each end of the 



■Ant&rwr End 



■Food Vacuole/ 

 ■Food Particl&s 



Canal 



Trichocyst 



Contractile Vacuole, Anterior 



uticle/ 

 ■Ectosarc 

 Food Vacuole/ 

 Etvdosarc 

 M&ganuchus 

 ■Micronucl&us 

 Oral Groove; 

 Food Vacuole; 

 ullbi 



Canal 



Food Vacuole 

 Food Parhcks 

 Vhdig&si&d Food 

 ntractile> Vacuole posterior 



Fig. 



7 ood Vacuole/ 

 ■Food Particles 



Posterior End 



52. Paramoecium caudatum. 

 (After Biitschli.) 



1 The early workers in biology took vegetable matter, such ar, dried grass, steeped it in boiling 

 water, and then left this infusion stand in the air. The animals found therein were called Infusoria. 



