188 Beekeeping 



Sex determination. 



The determination of sex is one of the most earnestly- 

 debated questions in zoology. Numerous theories have been 

 proposed, most of which are not now seriously considered. 

 From the observations and conclusions of Dzierzon and other 

 observers it was long held that sex in bees and similar forms 

 (ants and wasps) is determined by the presence or absence 

 of fertilization. ' These species were seemingly an exception 

 to the phenomenon observed in most species. Of recent 

 years, sex determination has been the object of numerous 

 investigations and it is now quite generally accepted that 

 sex is inherited in accordance with the same laws which govern 

 other phenomena of inheritance. It is, of course, impossible 

 to attempt to record here or even to outline the observations 

 which lead to this theory or to elaborate the theory, as has 

 been done by various authors. It is now held that one of 

 the chromosomes (the bearers of hereditary characters) of 

 the sex cells bears the sex-determining character. If we 

 take into consideration the important fact that not all the 

 eggs of an unfertihzed (drone-laying) queen hatch, then the 

 bee does not appear as an exception in Nature. It seems 

 clear, however, that the statement of Dzierzon that all the 

 eggs in the ovary are male eggs cannot be accepted and it is, 

 in fact, not improbable that the eggs destined to be females 

 die for want of fertilization, while the eggs destined to be 

 males, not requiring fertilization, are capable of development. 

 It should be understood that the casting of doubt on Dzier- 

 zon's theory of sex determination does not invalidate his 

 theory in so far as it pertains to the development of males 

 from unfertilized eggs. 



In view of the fact that drone eggs are usually deposited 

 in the larger cells, the theory has been advanced 'that the 

 pressure on the abdomen of the queen when she is about to 

 lay an egg in a worker cell, by some reflex, causes the sper- 

 matheca to open, thereby enabhng the egg to be fertilized. 

 This is known among American beekeepers as the Wagner 

 theory. Since fertiUzed eggs may be laid in comb foundation 



