760 EXPERIMENT STATION RECORD. 



testinal surface. The nuclei may fuse, or more often, the amcebula proceeds 

 to form daughter amcebulfe. The final active amcebulse are small, roundish 

 organisms, each with a single nucleus containing a karyosome. Each amoebula 

 is capable of amoeboid movement. It penetrates the cells of the gut, or else 

 between them, and finally either enters one of the cells or goes beyond and floats 

 in the hgemoccelic fluid. 



"Assuming tliat it enters an epithelial cell of the gut, it becomes rounded and 

 passive therein, and after a period of growth, during which time it is known 

 as a trophozoite, commences to multiply by several methods. There results 

 usually a collection of separate daughter individuals or meronts, or chains of 

 meronts. The chain condition is somewhat less common than the separate forms 

 in our experience so far. Each meront is uninucleate. Alternatively, a meront 

 may form a large, multinucleate body, in which cleavage into daughter meronts 

 does not occur. Such bodies may be intercellular or intracellular. 



"After a period of active growth and division producing uninucleate meronts, 

 spore formation begins. The organism is now called a pansporoblast. Active 

 amitotic nuclear division occurs, resulting in the production of 5 nuclei. 

 Two vacuoles also form in the developing spore, a large one at one end called 

 the posterior vacuole, and a small one at the opposite end, forming the polar 

 capsule. The living body substance or sporoplasm then forms a somewhat 

 ring-shaped mass between the 2 vacuoles, and in it are lodged the 5 nuclei 

 arising by division from the meront nucleus. Two migrate to the sides. These 

 become elongated, and may be termed the sporocyst nuclei. Of the other 3 

 nuclei, 1 controls for a time the polar capsule, and the other 2 the sporoplasm. 

 The polar capsule gradually forms the spiral polar filament, which extends 

 down into the posterior vacuole. While these nuclear changes are taking 

 place in the sporoblast or young spore, the latter is forming a coat around 

 itself. This spore coat or sporocyst gradually thickens and obscures the nuclei 

 beneath, and the final result is that from one pansporoblast a single spore, 

 resembling a rice grain in shape, with a shining refractile sporocyst is pro- 

 duced. In this condition the spore passes into the lumen of the gut, is voided 

 with the feces, and remains a source of infection for some time. 



" It will thus be realized that there are 2 distinct phases in the life cycle 

 of N. apis within the bee. This feature Nosema holds in common with other 

 protozoal parasites, such as the coccidium fatal to game birds and poultry. 

 The first part of the life of Nosema is occupied in gi-owth and active division, 

 so that the number of parasites within the host is enormously increased. 

 This multiplicative stage, known as merogony, is the one that is most dangerous 

 to the host. The young stages of the parasite alone are sufficient to kill the 

 bee in many cases, and the parasite as a result may never reach the final or 

 six)re stage of its development. Young grouse similarly are killed by the 

 multiplicative stages (merozoites) of Einicria {Coccidium) avium. 



" When the power of the parasite to multii)ly more in the one host is ex- 

 hausted or when the bee can no longer supply it with sufficient food, it becomes 

 necessary for the Nosema to leave its host and to renew its development in a 

 new one. Consequently, the parasite must protect itself in order to survive 

 the period between leaving one host and entering the next. As a result of this 

 need the parasite forms a hard outer covering or spore coat, and becomes a 

 spore. The spores are highly resistant to outside conditions, can live for some 

 time without losing their infective ix>wer, and so can become new sources of 

 infection for other bees. In other words, merogony of N. apis serves for the 

 infection of, and has fatal effects on, a single host; siiorogony is a means for 

 the spread of the disease to new hosts." 



