FOUNDATION OF A THEORY OF HEREDITY. 235 



has or has not taken place, respectively. Hence, one and the same 

 egg is capable of fertilization, and also of parthenogenetic develop- 

 ment, if it does not receive a spermatozoon. It is in the power of 

 the queen-bee to produce male or female individuals : by an act of 

 will she decides whether the egg- she is laying- is to be fertilized or 

 unfertilized. She 'knows beforehand '* whether an egg- will develope 

 into a male or a female animal, and deposits the latter kind in the 

 cells of queens and workers, the former in the cells of drones. It 

 has been shown by the discoveries of Leuckart and von Siebold that 

 all the eggs are capable of developing into male individuals, and 

 that they are only transformed into ' female eggs ' by fertilization. 

 This fact seems to be incompatible with my theory as to the cause 

 of parthenogenesis, for if the same egg, possessing exactly the same 

 contents, and above all the same segmentation nucleus, may de- 

 velope sexually or parthenogenetically, it appears that the power 

 of parthenogenetic development must depend on some factor other 

 than the quantity of germ-plasm. 



Although this appears to be the case, I believe that my theory 

 encounters no real difficulty. I have no doubt whatever, that the 

 same egg may develope with or without fertilization. From a care- 

 ful study of the numerous excellent investigations upon this point 

 which have been conducted in a particularly striking manner by 

 Bessels 2 (in addition to the observers quoted above), I have come 

 to the conclusion that the fact is absolutely certain. It must be 

 candidly admitted that the same egg will develope into a drone 

 when not fertilized, or into a worker or queen when fertilized. One 

 of Bessels' experiments is sufficient to prove this assertion. He 

 cut off the wings of a young queen and thus rendered her incapable 

 of taking ' the nuptial flight.' He then observed that all the eggs 

 which she laid developed into male individuals. This experiment 

 was made in order to prove that drones are produced by unfertilized 

 eggs ; but it also proves that the assertion mentioned above is correct, 

 for the eggs which ripen first and are therefore first laid, would have 



1 This expression is used by bee-keepers, for instance by the well-known Baron 

 Berlepsch. Of course, it would be more accurate to say that the queen, seeing the cell 

 of a drone, is stimulated to lay an unfertilized egg, and that, on the other hand, she 

 is stimulated to lay a fertilized egg when she sees the cell of a worker, or that of a 

 queen. 



2 E. Bessels, ' Die Landois'sche Theorie widerlegt durch das Experiment.' 

 Zeitschrift fur wissenschaftliche Zoologie, Bd. XVIII. p. 124. 1868. 



