8 BULLETIX 780, U. S. DEPARTMENT OF AGRICULTURE. 
ber 16. On the twenty-ninth of the same month all of the bees 
examined from the colony were found to be infected. The results 
of these experiments strongly indicated that the disorder in which 
the oval bodies were found was an infectious one and that the bodies 
were parasites which bore a causal relation to the disease. Other 
studies made by Donhoff (1857, September) indicated that the 
parasite was quite prevalent in Germany but that there were colonies 
apparently free from infection. 
About 50 years later Zander (1909) inoculated colonies experimen- 
tally by feeding material containing the oval bodies he had encoun- 
tered in his studies. In bees from the colonies inoculated he demon- 
strated that the oval bodies were in the walls of the stomach. This 
fact showed still more conclusively that there was an infectious 
disease of adult bees in which the oval bodies were parasites bearing 
a causal relationship to the disease. 
The oval bodies studied by Zander and those studied by Donhoff 
in all probability are the same. To Zander, however, is due the 
credit for having determined their true nature. Together with 
Doflein he (1909) classified the germ as a protozoan (a one-celled 
animal parasite) belonging to the group Microsporidia and to the 
genus Nosema. Zander gave the name Nosema apis to the species 
he found in the honeybee. 
The parasite 'Nosema apis grows and multiplies for the most part 
in the epithelium of the stomach (fig. 3 : Pis. II and III) of the adult 
bee. Occasionally, but rarely, it is found within the epithelial cells 
of the Malpighian tubules (Pis. II and III). When Nosema apis is 
encountered in making an examination for the parasite it is the spore 
form (fig. 4 ; PL III, G, H) that is most often encountered and most 
readily recognized. Viewed microscopically the spore in unstained 
preparations is seen to be a small, refractile, more or less oval body 
varying somewhat in size but measuring about 2/10,000 of an inch 
in length and about 1/10,000 of an inch in width. Its width seems, 
however, to be slightly greater than one-half its length. 1 The spore 
is surrounded by a somewhat resistant coat which tends to maintain 
for it a constant form. It is not, however, a rigid structure, since, 
when studied in fresh preparations, it will be seen to bend to and fro 
as it is carried along by a current under the cover glass. 
The manner in which a bee becomes infected with Nosema apis is 
in general as follows: Spores which have left the body of an infected 
bee with the excrement are ingested by the healthy adult bee. The 
environment within the stomach of the bee is favorable for the 
1 Measurements were made of spores in smears stained with iron hematoxylin and of others in prepara- 
tions made by an India-ink method. In making the latter preparations thin smears of the spore containing 
material were made and allowed to dry, and over these smears a thin film of undiluted India ink was spread. 
The average length of the spores measured in the stained preparations was 4.15 ti and the average breadth 
2.06 m; the average length in the India ink preparations was 4.46 ^ and the average breadth 2.44 p. 
