HOW YOUNG NOSEMA ARE KILLED 221 



It has been mentioned that several planonts may 

 invade the same cell, but they do not usually in- 

 vade it simultaneously. The result is that mature 

 spores, meronts engaged in active division, and 

 planonts may all be present at the same time in 

 one cell, so that crops of spores can be liberated 

 successively into the gut. It is worthy of note that 

 in many cases the injury to the intestinal wall, due 

 to the younger stages (meronts) of the parasite, are 

 so great that the bee dies as a result of their action. 

 In that case, the career of the parasite also comes 

 prematurely to an end, for hitherto all attempts at 

 infecting bees with the young stages of the parasites 

 have been failures. So far as our knowledge goes 

 at present, it is the spores, and the spores only, of 

 the parasite that are infective. The death of the 

 bee in which young, multiplicative stages of the 

 parasite occur, then, also terminates the existence of 

 the parasites. But in most cases a few at least of 

 the meront stages of Nosema apis are. carried farther, 

 and the parasites proceed to the formation of spores, 

 destined by their great powers of resistance to per- 

 petuate the race in yet another host. 



Now, according to the position of the meronts, 

 as single individuals or as numbers within a parent 

 meront, there is developed a single free spore or 

 a colony of several spores within the parent. The 

 meront which is about to become a spore is known 

 as a sporont or pansporoblast. It concentrates 

 its cytoplasm around its nucleus and gradually 

 alters its character and becomes the sporoblast. 

 This ceases to grow, secretes a spore coat or sporo- 



