240 CONTINUITY OF THE GERM-PLASM AS THE [IV. 



fertilization has or has not taken place, respectively. Hence, 

 one and the same egg is capable of fertilization, and also of 

 parthenogenetic development, if it does not receive a sperma- 

 tozoon. 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 be- 

 forehand ' ^ whether an ^^'g 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 ^gg^ possessing exactly the 

 same contents, and above all the same segmentation nucleus, 

 may develope 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 ^%g rna}'^ develope with or without fertilization. From 

 a careful study of the numerous excellent investigations upon 

 this point which have been conducted in a particularly striking 

 manner by Bessels^ (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 ^gg 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 3'oung 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 



' 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 un- 

 fertilized c^Zy 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. 



^ E. Bessels, ' Die Landois'schc llicoric widcrlcgt durch das Ex- 

 periment.' Zeitschrift fur wissenschaftliche Zoologie, Bd. XVIII. p. 124. 

 1868. 



