709 



without reaction, so that a few hours after the operation no traces 

 are distinguishable of tlie borders of the wound, even under the 

 microscope. Now in order to verify the extent of the rotated region 

 we had recourse to a special technique, which enabled us to recognize 

 the contour of the rotated patch for many days together (Trans- 

 plantation and vital staining after W, Vogt ')). 



The commencement of the ciliary movement in amphibian larvae 

 nearly coincides with the closure of the neural canal. When an 

 ectoderm region is rotated in a stage, in which the ciliary move- 

 ment has just commenced or has been proceeding for some time, 

 the ciliary movement will keep up its original direction. This lasts 

 for days until the ciliary cells disappear from the epidernii.s. An 

 infhience on the rotated region by its environment cannot be 

 made out. 



If tiie experiment is made after the conclusion of the gastrulaliou, 

 that is hours before the commencement of the ciliary movement, 

 the result is the same. So before the movement commences its direc- 

 tion has already been determined. 



Only in blastulae and the youngest gastrula stages can the future 

 ciliary movement be influenced successfully. 



From these experiments it may, therefore, be concluded that after 

 the conclusion of the gastriilatioii the polarity of the ciliated cell 

 has been determined. The following ex|)eriments were now made 

 with stages immediately succeeding the conclusion of the gastrulatioji. 

 I have extended the experiments to various spots that might be 

 considered as a .source of the ciliary movement. They were turned 

 long before the movement began. Nevertheless the process of the 

 ciliary movement in the non-rotated regions progressed quite normally. 



In another set of experiments vibrating patches of ectoderm were 

 implanted into young stages that did not yet possess ciliary move- 

 ment. Now it might lie supposed that on the appearance of the 

 movement, its direction would be dictated by that of the implantate. 

 In every experiment this influence failed to appear. 



Furthermore, non-vibrating patches of ectoderm (of very young 

 stages! were implanted into older larvae with vibrating epidermis. 



Now also it might be supposed that, when the ciliary movement 

 of the implantate commences, its direction would he determined by 

 the epidermis of the host. 



It appeared, however, that the ciliary movement nf the implant- 

 ate commenced simultaneouslv vvith the movement of the larva 



W. Vogt. Verhandl. deutsch. zool. Gesellsch. Bnd. '27. Sept. 1922. p. 49. 



