THE ABDOMEN. 



123 



On examination under the microscope, this is found 

 to be filled with a viscous fluid, in which, with a lens 

 of high power, may be seen moving thousands of 

 spermatozoa derived from the drone. By voluntary 

 effort on the part of the queen, each egg, as it passes 

 this vesicle, may be touched with a most minute drop 



FIG. 39. OVARIES AND SPERMATHECA OF QUEEN. 



of the fluid just mentioned. Then this very marvel- 

 lous fact results. An egg thus fertilised develops 

 into a queen or a worker, according to the conditions 

 under which it is hatched ; while those eggs which 

 are not brought in their passage into contact with 

 the fluid, and receive no spermatozoa, become 

 drones. Herein lies the explanation of fertile 

 workers giving birth to drones only, and of queens, 



