EXPERIMENTAL EMBRYOLOGY 



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of these potency regions during the time between the 12- and 24-hour 

 blastoderm. This, with a few preHminary experiments on an inter- 

 mediate stage, indicates that there is a gradual shifting of these bound- 

 aries out of the differentiation center and into their definitive position. 

 These facts suggest that the differentiation center bears a causal relation 

 to the development of the embryonic regions. The fact that a fixed 

 (morphological) region of the bee egg may have a prospective potency 

 in an early stage that is entirely different from (not merely more extensive 



aC12hrs.) b(Z4hrs.) 



Fig. 60. — Schematic anlagen plan of the honeybee egg. (a) Posterior boundaries of 

 the potency regions (" . . . those regions of which a small part must remain in the egg to 

 enable the formation of the entire corresponding organ region") in the 12-hour blastoderm. 

 (6) Expansion of the same regions along the longitudinal axis in the 24-hour blastoderm. 

 {Modified from Schnetter, 19346.) 



than) its prospective significance as shown in a later stage indicates that 

 chemo-differentiation is not only progressively increasing as development 

 proceeds but that there is also occurring a redistribution of the chemo- 

 differentiated materials. Furthermore, a shift in the region of first 

 visible differentiation in developing dwarfs following constrictions in the 

 12-hour stage (as evidenced by the more posterior position of the begin- 

 ning of the mesodermal furrows) indicates that this point assumes about 

 the same relative position in the decreased whole as in a normal egg. So 

 presumably dynamic factors are of fundamental importance in the egg 

 of the honeybee as well as Platycnemis. 



