LIFE-HISTORY OF NOSEMA APIS 217 



colonies always get attacked by robbers, the area of 

 infection is greatly extended. 



The life-history of Nosema apis may be conveni- 

 ently started at the time when the spores are ab- 

 sorbed by the bee either with its food or drink, or 

 when taken up in some other way that will be 

 discussed later. Infection takes place by way of the 

 mouth. The spores pass into the oesophagus, and 

 then into the honey stomach, or crop, where they 

 remain unchanged as a rule. When they enter the 

 chyle- or digesting stomach, the hard coat of each 

 spore is softened by the digestive juices, and a tiny 

 amoeboid germ creeps out into the cavity of the gut. 

 This amoebula gives rise, by division, to daughter 

 forms, each possessing one nucleus and capable of 

 wandering about over the epithelium of the gut 

 (Fig. 40, A). Such forms are called planonts, or 

 wanderers. The planonts creep about over the 

 epithelium (Fig. 40, B) for a short time, and may 

 increase in numbers by dividing into two, thus giving 

 rise to small colonies or nests of planonts. Gradually 

 the planonts penetrate between the cells, and finally 

 enter them, thus becoming intracellular (F"ig. 40, C). 

 The planonts, once they have entered their host cells, 

 become passive and gradually rounded or oval, and 

 are about 075 to 2'5 /* in diameter. The largest, 

 then, are about ^-^ of an inch across. The para- 

 sites proceed to grow and feed, becoming trophozoites. 

 The latter, after reaching a certain size, are capable 

 of division to produce new forms like themselves, and 

 thus from one original spore a large number of 

 descendants can arise. Not only is this the case, 



