352 The Unity of the Organism 



females, and males of the same species, readily occurred to 

 biologists, and a study of the subject has been made by sev- 

 eral investigators. The state of things found in the honey 

 bee, perhaps the most familiar example of virgin propaga- 

 tion, illustrates the principle involved. It has long been 

 known that female bees (queens and workers) are produced 

 from fertilized eggs, while males (drones) are produced from 

 non-fertilized eggs. If the dependence of sex on chromo- 

 somal peculiarities known to occur in some insects be true 

 generally, then the eggs of bees which develop partheno- 

 genetically might be expected to differ as to their chromo- 

 somes from those which develop after fertilization. This 

 expectation has been definitely realized. Before maturation 

 the male germ-cells have sixteen chromosomes and the fe- 

 male cell thirty-two. Reduction by one-half in the number 

 of chromosomes which occurs in typical spermatogenesis 

 does not take place here, so the spermatozoan receives the 

 full sixteen chromosomes. From this it results that the fer- 

 tilized egg, containing thirty-two chromosomes (sixteen hav- 

 ing been added by the spermatozoan), has undergone the 

 usual reduction of chromosome-number during maturation, 

 leaving it sixteen. "The fission spindle of the unfertilized 

 egg contains only the haploid number of chromosomes (16), 

 the fertilized egg contains naturally the diploid number 



"Here, then," says Doncaster, "is a clear case of sex 

 determined by, or at least in connection with, the presence 

 of a definite number of chromosomes ; when the full, or 

 double, number is present, the individual is a female; when 

 only the half number is present, it becomes a male." With 

 important variations for the different animal groups, the 

 first part of this statement has been found to be true for 

 quite a list of animals which reproduce parthenogenetically 

 a portion of the time, among these being certain wasps, 



