BALANTIDIUM 



519 



Nosema bombycis, the cause of silkworm disease (Pe*brine). The 

 organism forms many small spores each with one polar capsule. The 

 spores a iv carried 1>\ the food into the intestinal canal of the caterpillar, 

 pass through the walls of the intestines, and infect all organs. Spores 

 found in the ovary may be carried over to the newly hatched silkworms, 

 thus causing a further dissemination of the disease. 



The other member of this group of interest here is Nosema lophii 

 (I)oHein). Its interest lies in the fact that it has been found to infect only 

 the ganglion cells of the sea-devil, thus apparently resembling in its para- 

 sitic 1 nature the organism causing hydrophobia. 



Heterotricha. 



Class: Cilia ta. 



Order: Heterotricha. 



Genus: Balantidium. 



Balantidium coli (Malmst, 1857) . The body of this infusorium is egg- 

 shaped, with a funnel-shaped mouth opening. The surface of the body 

 is covered with a pellicula, under which is a distinct ectoplasmatic sheath 

 containing rows of basal granules from which the short, fine cilia arise. 



FIG. 159 



12 3 



Balantidium coli : 1, 2, stages of division ; 3, conjugation. (After Leuckart.) 



The cloudy entoplasm contains fat and starch granules and may 

 contain many red blood cells and other food particles from the host. 

 Two contractile vacuoles have been seen. Posteriorly there is a small 

 prominence marking the place where excreta are expelled. The chro- 

 matic macroniK'leus is bean-shaped, and the vesicular micronucleus 

 is nearly spherical. 



Division is transverse, the macronucleus dividing by simple con- 

 striction and the micronucleus by mitosis. Conjugation has been 

 observed. Spherical cysts surrounded by a thick membrane are formed. 



The balantidium coli has been found in the large intestine of human 

 beings and of swine probably two distinct varieties. The variety 



